TryBuildCalcAggregate Required for M20 Concrete (1:1.5:3 Concrete Aggregate Estimate)
Estimate aggregate required for M20 nominal concrete.
Use this M20 concrete aggregate calculator to estimate coarse aggregate quantity using a 1:1.5:3 nominal mix ratio.
🕒 Last updated: August 17, 2026
Inputs
Use this calculator when you know concrete volume and mix ratio. If you know the concrete element dimensions, switch to Dimensions mode and the calculator will first calculate concrete volume.
Need aggregate for road base, driveway, GSB, WMM, or area × depth? Use the Aggregate Coverage Calculator or Aggregate Weight Calculator.
ℹ️Selecting aggregate size updates the default ratio, aggregate part, and bulk density.
ℹ️For a 1:2:4 concrete ratio, the aggregate part is 4.
ℹ️Typical value is 1.54 for concrete and PCC aggregate estimation.
ℹ️Used to estimate weight from calculated loose aggregate volume.
Cost
For 1.000 m³ of concrete at a 1:1.5:3 ratio, you need approximately 0.882 m³ (31.2 cft) of 20mm aggregate — 1.37 tons.
Order Summary — Theoretical vs. Order Quantity
| Theoretical | Order Quantity | |
|---|---|---|
| Volume | 0.840 m³ | 0.882 m³ (31.2 cft) |
| Weight | 1,302 kg | 1,367 kg (1.37 tons) |
Theoretical = before wastage. Order Quantity = after your 5.0% wastage allowance. Round up to a supplier-friendly quantity — approx. 0.9 m³ or 1.4 tons.
Volume & Mix Details
Wet volume: 1.000 m³
Dry volume (×1.54): 1.540 m³
Ratio used: 1:1.5:3, aggregate part 3
Assumptions Used
Aggregate size: 20mm | Bulk density: 1,550 kg/m³ | Actual weight varies by aggregate size, stone type, moisture, and compaction.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Aggregate Calculator.
Aggregate for M20 nominal concrete
M20 nominal concrete is commonly estimated with a 1:1.5:3 ratio, where aggregate is the third (largest) part of the mix — this page preselects that ratio with the aggregate part set to 3.
Edit the volume above and the material breakdown and worked example update from the active values, still using the M20 mix ratio.
- M20 (1:1.5:3) needs approximately 0.83-0.84 m³ of aggregate per cubic metre before wastage.
- Aggregate part = 3, total parts = 5.5 for the M20 nominal ratio.
- For structural work, confirm the final mix design against your project's approved specification.
Step-by-step aggregate quantity calculation method
Aggregate quantity calculation starts with the required wet concrete volume. In Direct Volume mode, you enter that concrete volume directly. In Dimensions mode, the calculator first converts length, width, and depth/thickness into concrete volume. The calculator then converts wet volume into dry material volume, applies the selected mix ratio, calculates the aggregate share, and converts loose aggregate volume into approximate weight using bulk density.
For road base, driveway layers, GSB, WMM, or area × depth aggregate-only work, use the Aggregate Coverage Calculator or Aggregate Weight Calculator. This calculator is for concrete mix-ratio aggregate estimation.
Step 1 - Determine required concrete volume
Concrete volume is the finished wet concrete volume required for slabs, beams, columns, PCC, foundations, or other construction works. Enter it directly, or calculate it from dimensions.
Direct Volume Mode: Wet Volume = Entered Concrete Volume
Dimensions Mode: Wet Volume = Length × Width × Depth / Thickness
Step 2 - Convert wet volume to dry volume
Dry volume factor accounts for voids between aggregate particles, sand bulking, compaction, and practical site handling losses. For concrete and PCC estimation, a dry volume factor of 1.54 is commonly used.
Step 3 - Calculate aggregate share from mix ratio
The aggregate ratio part is divided by the total mix ratio parts to calculate the loose aggregate volume required for the selected concrete mix.
Step 4 - Convert aggregate volume to approximate weight
Bulk density converts loose aggregate volume into approximate aggregate weight. The default density changes automatically when you select 10mm, 20mm, or 40mm aggregate, and it can be adjusted for local material conditions.
Step 5 - Apply wastage allowance
Wastage allowance accounts for practical site losses during transport, unloading, storage, handling, and placement.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value | Why it is used |
|---|---|---|
| Concrete volume | 1 m³ | Sets the wet concrete volume to convert |
| Mix ratio / aggregate part | 1:1.5:3, part 3, ×1.54 | Splits dry volume into the aggregate share |
| Density / wastage | 1,550 kg/m³, 5% wastage | Converts volume to weight and adds a buffer for site losses |
Step 1 — Volume
| Calculation | Substitution | Result |
|---|---|---|
| Wet volume | 1 m³ | 1.000 m³ |
| Dry volume | 1.000 × 1.54 | 1.540 m³ |
Step 2 — Aggregate Quantity
| Calculation | Substitution | Result |
|---|---|---|
| Aggregate volume (theoretical) | 3 / 5.5 × 1.540 | 0.840 m³ |
| Aggregate weight (theoretical) | 0.840 × 1,550 | 1,302 kg |
| With 5% wastage | 0.840 × 1.05 | 0.882 m³ (1.37 tons) |
Therefore, plan for approximately 0.88 m³ (31.2 cft) — 1.37 tons — of 20mm aggregate for this pour.
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Disclaimer: This calculator provides approximate results for planning and estimation purposes only. Actual requirements may vary based on site conditions, materials, workmanship, and local building regulations. Always consult a qualified engineer, architect, or construction professional before making final decisions.