TryBuildCalcRoad Sub-Base Aggregate Calculator(Area, Thickness & Compaction)
Calculate aggregate for road sub-base.
🕒 Last updated: June 20, 2026
Inputs
ℹ️Auto-filled by material. Replace with supplier-tested density when available.
121.09 tonnes
121,094 kg
12% compaction allowance included
2,422 bags
143 × 850kg bulk bags
Rounded up to complete bags
Material: GSB (Granular Sub-Base)
Density: 1,700 kg/m³
Wastage: 6% included
Coverage Visualizations
Coverage Area
Layer Depth Cross-Section
Practical Coverage at 150.0mm Depth
After 6% wastage and 12% compaction allowance
Approximate results for planning only. Verify with a professional.
Road layer quantity from finished dimensions
Road construction often has separate GSB and WMM courses with different densities and compaction factors.
Run one calculation for each layer.
- Use surveyed finished area.
- Enter specified layer thickness.
- Apply material-specific compaction.
What Is an Aggregate Coverage Calculator?
Construction aggregate — crushed granite, GSB, WMM, limestone, river gravel — is ordered in tonnes or brass but placed in layers measured in millimetres. This calculator converts between the two in either direction for every major aggregate type used in civil and residential construction.
Whether you are estimating GSB sub-base coverage for a road project in India, checking how far a brass of 20mm aggregate will go for a concrete slab in Hyderabad, or sizing a MOT Type 1 layer for a UK driveway, this calculator gives you coverage area, required depth, or quantity needed — with options for compaction allowance, wastage, and concrete volume estimation.
Who uses this calculator:
- Civil and structural engineers sizing aggregate layers
- Site managers cross-checking sub-base material quantities
- Contractors comparing a supplier's brass quote against their drawing dimensions
- Homeowners planning a compacted driveway sub-base
- Road construction teams estimating GSB and WMM coverage
What makes this different from the Gravel Coverage Calculator:The Gravel Coverage Calculator is designed for landscaping and decorative applications. The Aggregate Coverage Calculator adds compaction factor correction for road base materials, brass unit input for Indian construction, and concrete volume estimation for coarse aggregate — features specifically needed for engineering and construction applications.
Applicable standards
- IS 383:2016 / IS 2386 — India (aggregate classification and testing)
- IRC SP:49 — India (road sub-base GSB/WMM specifications)
- BS EN 13242 — UK/Europe (unbound aggregates for road construction)
- ASTM D448 — USA (crushed aggregate size classification)
- AS 2758.1 — Australia (engineering aggregates)
How Is Aggregate Coverage Calculated?
Aggregate coverage is calculated from area, finished layer depth, bulk density, compaction allowance, and wastage. For loose aggregate layers, the calculation is similar to gravel coverage. For roadbase, GSB, WMM, crusher run, and MOT Type 1, the important difference is compaction: the loose delivered quantity must be higher than the finished compacted layer volume.
Use FIND QUANTITY when the area and finished depth are known and you want to calculate tonnes or bags. Use FIND AREA when aggregate quantity and finished depth are known and you want to calculate coverage area. Use FIND DEPTH when quantity and area are known and you want to check the achievable layer thickness.
Step 1 — Convert finished depth to metres
Depth (m) = Depth (mm) / 1,000
Aggregate layer depth must be in metres before volume is calculated. For example, a 150 mm sub-base layer is 150 / 1,000 = 0.15 m deep.
Step 2 — Calculate finished layer volume
Finished Volume (m³) = Area (m²) × Finished Depth (m)
If the area is 100 m² and the required finished depth is 150 mm, the finished volume is 100 × 0.15 = 15.00 m³. This is the compacted or final in-place volume required by the work.
Step 3 — Add compaction allowance for sub-base materials
Loose Volume = Finished Volume × (1 + Compaction / 100)
Compacted materials such as GSB, WMM, crusher run, and MOT Type 1 reduce in thickness and voids during rolling or plate compaction. If the finished volume is 15.00 m³ and compaction allowance is 12%, loose volume = 15.00 × 1.12 = 16.80 m³.
Step 4 — Convert loose volume into mass
Loose Mass (kg) = Loose Volume (m³) × Bulk Density (kg/m³)
Aggregate is usually ordered by tonnes. If loose volume is 16.80 m³ and density is 1,700 kg/m³, loose mass = 16.80 × 1,700 = 28,560 kg, or 28.56 tonnes before wastage.
Step 5 — Add wastage to calculate final order quantity
Order Mass = Loose Mass × (1 + Wastage / 100)
Wastage covers handling loss, trimming, edge loss, small level variation, and material left on the ground during spreading. Apply wastage after compaction allowance so the final quantity represents the amount to order.
Step 6 — Calculate coverage area when quantity is fixed
Coverage Area = Available Mass / [Density × Depth × (1 + Compaction / 100) × (1 + Wastage / 100)]
When quantity is fixed, compaction and wastage reduce the practical coverage area. For example, 20 tonnes of GSB will cover less area at 150 mm finished depth when 12% compaction and 6% wastage are included.
Step 7 — Calculate achievable depth from quantity and area
Finished Depth = Available Mass / [Area × Density × (1 + Compaction / 100) × (1 + Wastage / 100)]
This mode is useful when aggregate is already available on site. The calculator converts quantity into usable finished volume, divides it by the area, and returns the practical layer depth.
Optional — Estimate nominal M20 concrete yield
Concrete Volume = Aggregate Mass / (0.84 × Aggregate Density)
The 0.84 factor is a rough cross-check for the bulk coarse aggregate required per cubic metre of nominal 1:1.5:3 concrete. Use this only for approximate planning, not for structural concrete mix design.
Worked Aggregate Coverage Examples
The examples below show how to enter real site measurements into the aggregate coverage formula. Each example lists the calculator inputs first, then applies the formula step by step: calculate area, convert depth, calculate finished volume, adjust for compaction, convert to tonnes using bulk density, and add wastage where required.
Formula reminder: use FIND QUANTITY when area and depth are known, FIND AREA when quantity and depth are known, and FIND DEPTH when quantity and area are known. For compacted layers, calculate finished volume first, then add compaction allowance before converting to tonnes.
Example 1 — Calculate GSB Required for a Road Sub-Base
Calculator mode: FIND QUANTITY
A road sub-base is 50 m long and 8 m wide. The required finished compacted thickness is 150 mm. The selected material is GSB with an assumed loose bulk density of 1,700 kg/m³. A 12% compaction allowance is added to estimate loose material quantity, and a 6% wastage allowance is added for handling, trimming, edge loss, and level correction.
Input details
These are the values the user would enter or select in the calculator before reading the result.
| Input | Value | Why it matters |
|---|---|---|
| Calculator mode | FIND QUANTITY | Use this mode when the area and finished layer depth are known, and the calculator must find the aggregate quantity to order. |
| Material | GSB / granular sub-base | Well-graded sub-base aggregate used below road and pavement layers. |
| Bulk density | 1,700 kg/m³ | Used to convert loose aggregate volume into weight. |
| Length | 50 m | Road section length. |
| Width | 8 m | Road section width. |
| Finished depth | 150 mm | Required compacted layer thickness. |
| Compaction allowance | 12% | Allows for loose material reducing during compaction. |
| Wastage | 6% | Allows for handling loss, trimming, edge loss, and site variation. |
Step-by-step calculation
The table below shows how the input values are placed into the formula and converted into the final result.
| Step | Formula / Substitution | Result |
|---|---|---|
| Calculate area | Area = Length × Width | 50 × 8 = 400.00 m² |
| Convert depth to metres | Depth (m) = Depth (mm) / 1,000 | 150 / 1,000 = 0.15 m |
| Calculate finished volume | Finished Volume = Area × Finished Depth | 400.00 × 0.15 = 60.00 m³ |
| Add compaction allowance | Loose Volume = Finished Volume × 1.12 | 60.00 × 1.12 = 67.20 m³ |
| Convert loose volume to mass | Loose Mass = Loose Volume × Density | 67.20 × 1,700 = 114,240 kg |
| Convert to tonnes before wastage | Tonnes = kg / 1,000 | 114,240 / 1,000 = 114.24 tonnes |
| Add wastage | Order Mass = Loose Mass × 1.06 | 114,240 × 1.06 = 121,094 kg |
| Final tonnes | Final Tonnes = 121,094 / 1,000 | 121.09 tonnes |
Result
The 50 m × 8 m GSB road sub-base requires approximately 121.09 tonnes of aggregate, assuming 150 mm finished compacted depth, 12% compaction allowance, and 6% wastage.
Practical note
For road layers, the required depth is usually a compacted finished thickness. Loose delivery quantity must allow for compaction. Always check the project specification, compaction method, layer thickness, and field density requirement before final ordering.
Example 2 — Calculate MOT Type 1 Required for a Car Park Sub-Base
Calculator mode: FIND QUANTITY
A car park area is 600 m². The required finished compacted sub-base thickness is 200 mm. The selected material is MOT Type 1 / crusher run with an assumed loose bulk density of 1,900 kg/m³. A 20% compaction allowance and 5% wastage allowance are used.
Input details
These are the values the user would enter or select in the calculator before reading the result.
| Input | Value | Why it matters |
|---|---|---|
| Calculator mode | FIND QUANTITY | Use this mode when the car park area and sub-base depth are known. |
| Material | MOT Type 1 / crusher run | Dense graded sub-base material containing coarse aggregate and fines. |
| Bulk density | 1,900 kg/m³ | Used to convert loose volume into weight. |
| Area | 600 m² | Measured car park area. |
| Finished depth | 200 mm | Required compacted sub-base thickness. |
| Compaction allowance | 20% | Allows for loose material reducing during compaction. |
| Wastage | 5% | Allows for trimming, spreading loss, and uneven subgrade correction. |
Step-by-step calculation
The table below shows how the input values are placed into the formula and converted into the final result.
| Step | Formula / Substitution | Result |
|---|---|---|
| Use measured area | Area = 600 m² | 600.00 m² |
| Convert depth to metres | Depth (m) = Depth (mm) / 1,000 | 200 / 1,000 = 0.20 m |
| Calculate finished volume | Finished Volume = Area × Finished Depth | 600.00 × 0.20 = 120.00 m³ |
| Add compaction allowance | Loose Volume = Finished Volume × 1.20 | 120.00 × 1.20 = 144.00 m³ |
| Convert loose volume to mass | Loose Mass = Loose Volume × Density | 144.00 × 1,900 = 273,600 kg |
| Convert to tonnes before wastage | Tonnes = kg / 1,000 | 273,600 / 1,000 = 273.60 tonnes |
| Add wastage | Order Mass = Loose Mass × 1.05 | 273,600 × 1.05 = 287,280 kg |
| Final tonnes | Final Tonnes = 287,280 / 1,000 | 287.28 tonnes |
Result
The car park sub-base requires approximately 287.28 tonnes of MOT Type 1 / crusher run after compaction allowance and wastage.
Practical note
This example shows why compacted sub-base quantities become large quickly. A 200 mm finished layer over 600 m² equals 120 m³ before compaction adjustment. For large paved areas, even a small change in depth has a major effect on tonnage.
Example 3 — Check Coverage Area from a Fixed Aggregate Quantity
Calculator mode: FIND AREA
A contractor has 20 tonnes of GSB available and wants to know how much area it can cover at 150 mm finished compacted depth. The assumed loose bulk density is 1,700 kg/m³. A 12% compaction allowance and 6% wastage allowance are considered.
Input details
These are the values the user would enter or select in the calculator before reading the result.
| Input | Value | Why it matters |
|---|---|---|
| Calculator mode | FIND AREA | Use this mode when aggregate quantity and finished depth are known, and the calculator must find coverage area. |
| Material | GSB / granular sub-base | Used for road and pavement sub-base layers. |
| Bulk density | 1,700 kg/m³ | Used to convert available mass into loose volume. |
| Quantity | 20 tonnes | Available aggregate quantity. |
| Finished depth | 150 mm | Target compacted layer thickness. |
| Compaction allowance | 12% | Reduces practical coverage because extra loose material is needed for compaction. |
| Wastage | 6% | Reduces practical coverage because some material is lost or used in trimming and level correction. |
Step-by-step calculation
The table below shows how the input values are placed into the formula and converted into the final result.
| Step | Formula / Substitution | Result |
|---|---|---|
| Convert tonnes to kg | Mass = Tonnes × 1,000 | 20 × 1,000 = 20,000 kg |
| Calculate loose volume available | Loose Volume = Mass / Density | 20,000 / 1,700 = 11.765 m³ |
| Remove wastage allowance | Usable Loose Volume = Loose Volume / 1.06 | 11.765 / 1.06 = 11.099 m³ |
| Convert loose volume to finished volume | Finished Volume = Usable Loose Volume / 1.12 | 11.099 / 1.12 = 9.910 m³ |
| Convert depth to metres | Depth (m) = Depth (mm) / 1,000 | 150 / 1,000 = 0.15 m |
| Calculate coverage area | Area = Finished Volume / Depth | 9.910 / 0.15 = 66.07 m² |
Result
20 tonnes of GSB covers approximately 66.1 m² at 150 mm finished compacted depth after allowing for 12% compaction and 6% wastage.
Practical note
When quantity is fixed, compaction and wastage reduce the practical area covered. The calculator should not show the same coverage area before and after these allowances.
Example 4 — Check Finished Depth from a Fixed Quantity and Area
Calculator mode: FIND DEPTH
A user has 30 tonnes of 20 mm crushed aggregate and wants to spread it over a 120 m² area. The aggregate density is assumed to be 1,600 kg/m³. A 5% wastage allowance is applied. No compaction allowance is used because this example is for loose aggregate coverage, not compacted roadbase.
Input details
These are the values the user would enter or select in the calculator before reading the result.
| Input | Value | Why it matters |
|---|---|---|
| Calculator mode | FIND DEPTH | Use this mode when aggregate quantity and area are known, and the calculator must find achievable depth. |
| Material | 20 mm crushed aggregate | Common coarse aggregate used for construction, drainage, and general filling. |
| Bulk density | 1,600 kg/m³ | Used to convert aggregate mass into volume. |
| Quantity | 30 tonnes | Available aggregate quantity. |
| Area | 120 m² | Area to cover. |
| Wastage | 5% | Used to estimate practical depth after spreading and handling loss. |
| Compaction allowance | 0% | No compaction allowance used in this loose aggregate example. |
Step-by-step calculation
The table below shows how the input values are placed into the formula and converted into the final result.
| Step | Formula / Substitution | Result |
|---|---|---|
| Convert tonnes to kg | Mass = Tonnes × 1,000 | 30 × 1,000 = 30,000 kg |
| Calculate loose volume | Volume = Mass / Density | 30,000 / 1,600 = 18.750 m³ |
| Remove wastage allowance | Usable Volume = Volume / 1.05 | 18.750 / 1.05 = 17.857 m³ |
| Use measured area | Area = 120 m² | 120.00 m² |
| Calculate depth in metres | Depth = Usable Volume / Area | 17.857 / 120 = 0.1488 m |
| Convert depth to mm | Depth (mm) = Depth (m) × 1,000 | 0.1488 × 1,000 = 148.8 mm |
Result
30 tonnes of 20 mm crushed aggregate spread over 120 m² gives approximately 149 mm practical depth after a 5% wastage allowance.
Practical note
FIND DEPTH is useful when material is already available on site and the user wants to check whether it can achieve the required layer thickness.
Example 5 — Convert Three Brass of 20 mm Aggregate to Tonnes
Calculator mode: FIND QUANTITY
A supplier quotes 3 brass of 20 mm aggregate. The user wants to convert this volume into tonnes. One brass is taken as 100 cubic feet, or approximately 2.832 m³. The assumed aggregate density is 1,600 kg/m³.
Input details
These are the values the user would enter or select in the calculator before reading the result.
| Input | Value | Why it matters |
|---|---|---|
| Calculator mode | FIND QUANTITY | Use this mode when a volume quantity is known and the calculator must estimate weight. |
| Material | 20 mm aggregate | Common crushed coarse aggregate. |
| Bulk density | 1,600 kg/m³ | Used to convert volume into mass. |
| Quantity | 3 brass | Local volume-based aggregate quantity. |
| Conversion | 1 brass = 2.832 m³ | Used to convert brass into cubic metres. |
| Wastage | 0% | No wastage added in this simple unit conversion example. |
Step-by-step calculation
The table below shows how the input values are placed into the formula and converted into the final result.
| Step | Formula / Substitution | Result |
|---|---|---|
| Convert brass to cubic metres | Volume = Brass × 2.832 | 3 × 2.832 = 8.496 m³ |
| Convert volume to mass | Mass = Volume × Density | 8.496 × 1,600 = 13,594 kg |
| Convert kg to tonnes | Tonnes = kg / 1,000 | 13,594 / 1,000 = 13.59 tonnes |
Result
Three brass of 20 mm aggregate is approximately 8.496 m³, which equals about 13.59 tonnes at 1,600 kg/m³.
Practical note
Brass is a volume unit, while many suppliers quote aggregate by tonnes. The conversion depends on density, so 3 brass of lightweight aggregate and 3 brass of dense crushed stone will not weigh exactly the same.
Example 6 — Estimate Nominal M20 Concrete Yield from Aggregate Quantity
Calculator mode: OPTIONAL CONCRETE YIELD CHECK
A user has approximately 13.59 tonnes of 20 mm aggregate and wants to estimate how much nominal M20 concrete it could produce. This is only a cross-check, not a structural mix design. The assumed aggregate density is 1,600 kg/m³ and the calculator uses a 0.84 coarse-aggregate factor for nominal 1:1.5:3 concrete.
Input details
These are the values the user would enter or select in the calculator before reading the result.
| Input | Value | Why it matters |
|---|---|---|
| Calculator mode | Optional concrete yield | Use this only as a rough cross-check when aggregate is being related to nominal concrete quantity. |
| Material | 20 mm aggregate | Coarse aggregate used in nominal M20 concrete. |
| Aggregate mass | 13,594 kg | Mass calculated from 3 brass in the previous example. |
| Aggregate density | 1,600 kg/m³ | Used with the 0.84 factor to estimate concrete yield. |
| Coarse aggregate factor | 0.84 | Approximate bulk coarse aggregate per 1 m³ of nominal 1:1.5:3 concrete. |
Step-by-step calculation
The table below shows how the input values are placed into the formula and converted into the final result.
| Step | Formula / Substitution | Result |
|---|---|---|
| Use aggregate mass | Aggregate Mass = 13,594 kg | 13,594 kg |
| Calculate denominator | 0.84 × Aggregate Density | 0.84 × 1,600 = 1,344 kg per m³ |
| Estimate concrete volume | Concrete Volume = Aggregate Mass / (0.84 × Aggregate Density) | 13,594 / 1,344 = 10.11 m³ |
Result
13.59 tonnes of 20 mm aggregate can produce approximately 10.11 m³ of nominal M20 concrete by this rough cross-check method.
Practical note
This is not a replacement for concrete mix design. For RCC or structural work, use an approved mix design or project specification. Cement, sand, water, moisture correction, grading, and bulking must also be considered.
Aggregate Coverage Reference Tables
Coverage per Tonne at Common Depths
| Aggregate Type | Density | 50mm | 100mm | 150mm | 200mm | 300mm |
|---|---|---|---|---|---|---|
| 20mm Crushed Granite | 1,600 | 12.5m² | 6.25m² | 4.17m² | 3.13m² | 2.08m² |
| 40mm Crushed Granite | 1,550 | 12.9m² | 6.45m² | 4.30m² | 3.23m² | 2.15m² |
| Crushed Limestone (20mm) | 1,490 | 13.4m² | 6.71m² | 4.47m² | 3.36m² | 2.24m² |
| River Gravel (20mm) | 1,500 | 13.3m² | 6.67m² | 4.44m² | 3.33m² | 2.22m² |
| GSB (Granular Sub-Base) | 1,700 | 11.8m² | 5.88m² | 3.92m² | 2.94m² | 1.96m² |
| WMM (Wet Mix Macadam) | 1,800 | 11.1m² | 5.56m² | 3.70m² | 2.78m² | 1.85m² |
| MOT Type 1 / Crusher Run | 1,900 | 10.5m² | 5.26m² | 3.51m² | 2.63m² | 1.75m² |
| DGA / Quarry Process | 1,900 | 10.5m² | 5.26m² | 3.51m² | 2.63m² | 1.75m² |
| Single-size Drainage Gravel | 1,480 | 13.5m² | 6.76m² | 4.50m² | 3.38m² | 2.25m² |
| RCA (Recycled Concrete) | 1,350 | 14.8m² | 7.41m² | 4.94m² | 3.70m² | 2.47m² |
Per 1 tonne using finished, uncompacted dimensions. Add the specified compaction factor for GSB, WMM, and road base.
Coverage per Brass at Common Depths
1 brass = 2.832m³. Coverage per brass is the same for every material because brass is a volume unit.
| Material | Density | 100mm | 150mm | 200mm |
|---|---|---|---|---|
| 20mm Crushed Granite | 1,600 | 28.3m² | 18.9m² | 14.2m² |
| 40mm Crushed Granite | 1,550 | 28.3m² | 18.9m² | 14.2m² |
| GSB | 1,700 | 28.3m² | 18.9m² | 14.2m² |
| WMM | 1,800 | 28.3m² | 18.9m² | 14.2m² |
| River Gravel | 1,500 | 28.3m² | 18.9m² | 14.2m² |
Concrete Volume per Tonne of Aggregate—M20 Nominal Mix
| Aggregate Type | Density | Per Tonne | Per Brass | Per 10T Truck |
|---|---|---|---|---|
| 20mm Granite (M20 coarse) | 1,600 | 0.744m³ concrete | 2.11m³ | 7.44m³ |
| River Gravel (M20 coarse) | 1,500 | 0.744m³ concrete | 2.11m³ | 7.44m³ |
| M Sand (M20 fine) | 1,750 | 1.420m³ concrete | 4.02m³ | 14.2m³ |
Based on nominal M20 proportions: coarse aggregate = 0.84m³ bulk and fine aggregate = 0.44m³ bulk per cubic metre of concrete.
Compaction Factors by Aggregate Type
| Material | Standard | Compaction Factor | Notes |
|---|---|---|---|
| GSB Grade I | IRC SP:49 | 12–15% | Machine compaction required |
| GSB Grade II | IRC SP:49 | 12–15% | Machine compaction required |
| WMM | IRC MoRT&H | 10–13% | Roller compaction |
| MOT Type 1 | Highways England SHW | 15–20% | Plate compactor or roller |
| MOT Type 2 | Highways England SHW | 12–18% | Less dense grading |
| DGA / QP | ASTM D698 | 15–20% | Proctor compaction |
| Roadbase (Australia) | AS 1289 | 15–20% | Standard compaction |
| Drainage gravel | N/A | 0% | Must not be compacted |
| Concrete aggregate | N/A | 0% | Batched by weight |
Standard Layer Thicknesses by Application
| Application | Layer | Typical Thickness | Standard |
|---|---|---|---|
| Residential driveway | GSB sub-base | 100–150mm | Advisory |
| Residential driveway | MOT Type 1 | 150–200mm | Advisory |
| Light commercial | GSB sub-base | 200–250mm | IRC / Advisory |
| Rural road | GSB + WMM | 200mm GSB + 75mm WMM | IRC / Advisory |
| Building plinth | PCC blinding | 75–100mm | IS 456 |
| RCC slab | Blinding / PCC | 50–75mm | IS 456 |
| Pipe trench | Bedding | 100mm | Site-specific |
| Soakaway | Fill | 500mm–full depth | Site-specific |
Essential Checklist+−
Complete these critical checks before approving the work or proceeding to the next construction stage.
✓Area Measurement+-
- All dimensions were measured on site — not scaled from drawings or estimated.
- Irregular areas were divided into simple shapes (rectangles, triangles) and each measured separately.
✓Depth and Layer+-
- The depth entered is the compacted (finished) layer thickness, not the loose spread thickness.
- Layer depth is confirmed from the structural or pavement design drawings — not assumed.
- Depth is entered in the correct unit — mm not cm, or cm not m.
- For multi-layer pavement (GSB + WMM + wearing course), each layer is calculated separately.
✓Aggregate Type and Specification+-
- Aggregate type matches the application — GSB for sub-base, WMM for road base, single-size for drainage, crushed stone for concrete.
- Drainage aggregate is single-size with less than 5% fines — graded aggregate blocks drainage voids.
- GSB and WMM are well-graded (0 to maximum size) — single-size stone must not be used for compacted road layers.
- Bulk density used in the calculator matches the specific aggregate type — GSB 1,700 kg/m³, MOT Type 1 1,900 kg/m³, pea gravel 1,500 kg/m³.
✓Compaction+-
- Compaction factor is applied for all layers that will be mechanically compacted after placing.
- Compaction factor is set to 0% for single-size drainage aggregate — compacting drainage aggregate destroys its void structure.
- Compaction factor is not applied to aggregate for concrete batching — concrete aggregate is batched by weight, not loose volume.
✓Wastage+-
- A minimum wastage of 5% is applied for all machine-spread aggregate.
- The quantity with wastage — not the net coverage quantity — is used for ordering.
✓Coverage Output Check+-
- The coverage area in the result is within 5% of the independently measured site area.
- The delivery unit in the result (tonne, brass, cubic metre, truck load) matches what the supplier quotes.
✓Before Purchase+-
- Supplier bulk density for the specific aggregate batch was confirmed and matches the value used in the calculator.
- Separate calculations were completed for each aggregate layer or application type on the same project.
Full QC Checklist+−
Use this checklist before relying on the aggregate coverage estimate.
✓Area Measurement+-
- All dimensions were measured on site — not scaled from drawings or estimated.
- Irregular areas were divided into simple shapes (rectangles, triangles) and each measured separately.
- Fixed exclusions (columns, drains, cast-in fixtures) were deducted from the gross area.
- For road or pavement areas, carriageway width was measured at the narrowest point.
✓Depth and Layer+-
- The depth entered is the compacted (finished) layer thickness, not the loose spread thickness.
- Layer depth is confirmed from the structural or pavement design drawings — not assumed.
- Depth is entered in the correct unit — mm not cm, or cm not m.
- For multi-layer pavement (GSB + WMM + wearing course), each layer is calculated separately.
- Concrete blinding (PCC) depth is a minimum of 75mm below footings as per IS 456:2000.
- Road wearing course thickness does not exceed the design specification — excess depth adds weight without structural benefit.
✓Aggregate Type and Specification+-
- Aggregate type matches the application — GSB for sub-base, WMM for road base, single-size for drainage, crushed stone for concrete.
- Drainage aggregate is single-size with less than 5% fines — graded aggregate blocks drainage voids.
- GSB and WMM are well-graded (0 to maximum size) — single-size stone must not be used for compacted road layers.
- Aggregate nominal size is appropriate — 20mm for concrete, 40mm for PCC and sub-base, 10mm for filter layers.
- Aggregate source and grading comply with IS 383:2016 (India), ASTM C33 (USA), or BS EN 12620 (UK/EU) as applicable.
- Bulk density used in the calculator matches the specific aggregate type — GSB 1,700 kg/m³, MOT Type 1 1,900 kg/m³, pea gravel 1,500 kg/m³.
✓Compaction+-
- Compaction factor is applied for all layers that will be mechanically compacted after placing.
- Compaction factor is set to 0% for single-size drainage aggregate — compacting drainage aggregate destroys its void structure.
- Compaction factor is not applied to aggregate for concrete batching — concrete aggregate is batched by weight, not loose volume.
- Typical compaction factors: GSB 12–15%, WMM 10–13%, MOT Type 1 sub-base 15–25%, backfill 8–12%.
- Number of compaction passes and equipment type are confirmed with the contractor before placing the order.
✓Wastage+-
- A minimum wastage of 5% is applied for all machine-spread aggregate.
- Wastage is increased to 8–12% for hand-spread aggregate, drainage trenches, and irregular excavation edges.
- Road sub-base wastage of 5–7% accounts for mechanical spreading overshoot and truck bed residue.
- The quantity with wastage — not the net coverage quantity — is used for ordering.
✓Coverage Output Check+-
- The coverage area in the result is within 5% of the independently measured site area.
- The result was cross-checked using a manual calculation: area × depth × bulk density × compaction factor × wastage factor.
- The delivery unit in the result (tonne, brass, cubic metre, truck load) matches what the supplier quotes.
- Truck capacity was confirmed with the supplier before using the truck-load count in the result.
✓Before Purchase+-
- Supplier bulk density for the specific aggregate batch was confirmed and matches the value used in the calculator.
- Aggregate grading certificate (sieve analysis) was requested for structural and road applications.
- Delivery scheduling matches the construction programme — aggregate stored on site more than 2 weeks risks contamination.
- Site access for delivery vehicles (turning radius, axle load limit on access road) was confirmed.
- Currency and units match the supplier quotation.
- Delivery charges, state levies, and taxes were confirmed separately.
- Separate calculations were completed for each aggregate layer or application type on the same project.
Tips for Accurate Aggregate Coverage
Brass is a volume unit—its weight depends on material
Five brass equals 14.16m³. At 1,700kg/m³, that is about 24 tonnes of GSB; at 1,900kg/m³, it is about 26.9 tonnes of MOT Type 1. Coverage per brass is constant at a given depth, but weight and cost vary significantly.
Always apply compaction factor to sub-base quantities
A 150mm compacted GSB layer requires ordering the equivalent of roughly 168–173mm loose material at 12–15% compaction. Calculating only from finished dimensions is a common cause of shortages.
RCA covers more area per tonne—but verify density
Recycled Concrete Aggregate may range from about 1,100–1,400kg/m³. It covers more area per tonne than virgin granite, but its quantity estimate is less certain. Use a supplier-tested custom density.
Drainage aggregate must not be compacted
Single-size drainage and filter gravel depends on 38–45% interconnected voids. Compaction reduces those voids and damages drainage performance, so set compaction to 0%.
Use concrete coverage as a cross-check
If the nominal M20 concrete-yield output does not align with the Concrete Mix Calculator for the same project, review the aggregate quantity or mix assumptions before procurement.
Calculator Limitations & Assumptions
- Concrete coverage uses nominal M20 mix only: the 1:1.5:3 assumption will not match a design mix. Use the Concrete Mix Calculator for design-mix quantities.
- Compaction factors are typical ranges: actual values depend on gradation, equipment, moisture, and passes. Follow the project geotechnical specification for structural bases.
- Coverage assumes a regular area: divide road curves, irregular embankments, and tapered sections into measured sub-sections.
- Density varies by quarry: for orders above about 50 tonnes, use supplier-tested bulk density rather than reference values.
- RCA properties are highly variable: recycled material varies by demolition source in density, absorption, and gradation. Use a tested custom value.