TryBuildCalcFloor Screed Calculator (Cement & Sand for Flooring)
Calculate screed cement and sand instantly.
🕒 Last updated: August 23, 2026
Inputs
ℹ️Typical: 38-50 mm (bonded/unbonded), 65-75 mm (floating/underfloor heating)
Cost
For 20.00 m² of floor area, you need approximately 9 cement bags and 1.12 m³ of sand.
Screed Volume
Floor area: 20.00 m²
Wet volume: 1.000 m³
Dry volume (×1.33): 1.330 m³
Materials
Cement: 8.1 bags — buy 9 bags
Sand: 1.117 m³ (~1.79 metric tons)
Sand tonnage is approximate, using 1.6 tons/m³ average bulk density.
Order Summary — Theoretical vs. Order Quantity
| Material | Theoretical | Order Quantity |
|---|---|---|
| Cement | 7.7 bags | 9 bags (whole) |
| Sand | 1.064 m³ | 1.117 m³ |
Theoretical = before wastage. Order Quantity = after your 5.0% wastage allowance (cement rounded up to a whole bag).
Assumptions Used
Dry volume factor: 1.33 | Cement bag: 50 kg / 0.0347 m³ | Wastage applied once to cement bags and sand volume.
Bonded, unbonded, or floating — not sure which screed type applies here? Floor Screed Guide →
Tiling this floor once the screed has cured and dried? Tile Calculator →
What Is a Floor Screed Calculator?
A floor screed calculator estimates the quantity of cement and sand required to lay a screed layer over a structural slab or PCC base, based on floor area, screed thickness, and the selected cement:sand mix ratio. It is commonly used by civil engineers, contractors, builders, and homeowners to plan material procurement and construction budgeting before starting flooring work.
Unlike a bare area calculator, this tool applies dry volume correction and mix ratio distribution to give realistic cement and sand quantities matching what you would actually order or mix on site — not just a raw area-times-thickness figure.
Why accurate screed estimation matters:
- Avoid material shortages and cold joints mid-way through a screed bay
- Reduce excess cement and sand wastage and cost
- Improve project cost planning and scheduling
- Ensure the correct mix ratio and thickness for a durable, tile-ready surface
- Prevent delays caused by re-ordering material mid-job
Floor Screed Formula: How Is Cement and Sand Quantity Calculated?
Screed quantity is calculated from floor area and thickness, converted into dry volume, then distributed according to the cement:sand mix ratio.
Step 1 — Floor Area & Wet Volume
Floor Area = Length × Width
Wet Volume = Floor Area × Screed Thickness
Floor area is the plan area to be screeded. Wet volume is the actual mixed-screed volume needed to cover that area at the specified thickness.
Step 2 — Dry Volume Correction
Dry Volume = Wet Volume × 1.33
The dry volume factor accounts for sand bulking, voids between materials, and practical construction losses during mixing and application. Screed uses 1.33 rather than concrete's 1.54 because it contains no coarse aggregate.
Step 3 — Mix Ratio Distribution
Cement Volume = Dry Volume × (Cement Part ÷ Total Parts)
Sand Volume = Dry Volume × (Sand Part ÷ Total Parts)
Dry screed volume is divided according to the selected cement:sand mix ratio — 1:3 (heavy-duty industrial), 1:4 (standard), or 1:5 (light leveling only). Total Parts is the sum of both ratio parts.
Step 4 — Cement Bags Conversion
Cement Bags = Cement Volume ÷ 0.0347 m³/bag (50 kg bags)
One standard cement bag (50 kg) occupies approximately 0.0347 cubic metres. This conversion translates calculated cement volume into practical material procurement quantities.
Step 5 — Final Quantity with Wastage
Final Cement Bags = Cement Bags × (1 + Wastage %), rounded up to a whole bag
Final Sand Volume = Sand Volume × (1 + Wastage %)
Wastage is applied to both cement bags and sand volume for the practical order quantity — shown separately from the theoretical pre-wastage figures in the result card.
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 |
|---|---|---|
| Length × width | 5m × 4m | Sets the floor area to be screeded |
| Thickness / mix ratio / wastage | 50mm, 1:4, 5% wastage | Sets wet volume and splits dry volume into cement/sand |
Step 1 — Area & Volume
| Calculation | Substitution | Result |
|---|---|---|
| Floor area | 5m × 4m | 20.00 m² |
| Wet volume | 20.00 × 50mm | 1.000 m³ |
| Dry volume | 1.000 × 1.33 | 1.330 m³ |
Step 2 — Cement & Sand
| Material | Theoretical | Order Quantity |
|---|---|---|
| Cement | 7.7 bags | 9 bags (whole) |
| Sand | 1.064 m³ | 1.117 m³ |
Therefore, for 20.00 m² of floor at 50mm screed thickness and a 1:4 mix, you need approximately 9 cement bags and 1.12 m³ of sand.
Essential Checklist+−
Complete these critical checks before approving the work or proceeding to the next construction stage.
✓Volume Estimation & Mix Selection+-
- Screed area measured on site — gross area with deductions for columns, walls, and fixed items
- Screed thickness confirmed from floor level drawing — accounts for tile, flooring, and finished floor level
- Screed type confirmed — bonded, unbonded, or floating; conventional or semi-dry
- Screed mix ratio confirmed — 1:3 to 1:4 cement:sand for conventional screed
- Dry volume factor of 1.33 applied — screed is a mortar (no coarse aggregate)
- Wastage of 10–15% added to screed volume
✓Substrate Preparation+-
- Structural slab cleaned of all dust, laitance, oil, and curing compound before screed
- For bonded screed — slab surface mechanically prepared and bonding slurry applied
- For unbonded screed — DPM (250-micron polythene) laid flat, lapped 300mm, turned up at edges
- For floating screed — insulation boards flat, fully supported, joints staggered
- Perimeter isolation strips installed at all walls, columns, and fixed elements before screed
- All floor services (underfloor heating, conduits, pipes) installed and tested before screed
- Structural slab level surveyed — high and low points identified, screed thickness variation managed
✓Laying & Level Control+-
- Screed rails or dots set to correct finished screed level across full floor area
- Laser level or optical level used to confirm finished screed level at multiple points
- Semi-dry screed consistency correct — holds shape when squeezed in the fist without releasing free water
- Screed bays planned — maximum 40 m² per bay, or 8m maximum dimension
- Screed fully compacted — tamped or rolled to close voids before floating
✓Curing & Protection+-
- Screed curing started within 24 hours — polythene sheet or damp hessian applied
- Screed cured for minimum 7 days — polythene or wet hessian maintained throughout
- No foot traffic for 24 hours; no point loads or stacked materials for 7 days
- Screed confirmed dry before floor finish is applied — minimum 1 day per mm thickness
- Screed inspected for cracking after curing — hairline cracks logged, wide cracks investigated
✓Quality Checks & Defect Prevention+-
- Screed flatness checked with 3m straightedge — deviation within ±3mm for tiled floors
- Screed hollow test performed — tap entire screed systematically before floor finish
- Structural expansion joints in slab continued through screed — not bridged
Full QC Checklist+−
Verification checklist for floor screed estimation and laying — covering volume calculation, mix selection, substrate preparation, laying sequence, level control, curing, and defect prevention. Use the Essential Checklist for critical checks before and during screed laying; expand to Full QC Checklist for complete screed quality control from substrate through finished surface.
✓Volume Estimation & Mix Selection+-
- Screed area measured on site — gross area with deductions for columns, walls, and fixed items
- Screed thickness confirmed from floor level drawing — accounts for tile, flooring, and finished floor level
- Screed type confirmed — bonded, unbonded, or floating; conventional or semi-dry
- Screed mix ratio confirmed — 1:3 to 1:4 cement:sand for conventional screed
- Dry volume factor of 1.33 applied — screed is a mortar (no coarse aggregate)
- Wastage of 10–15% added to screed volume
- Calculated quantities checked against reference — 50mm screed at 1:4 requires approximately 3.8 bags cement per 10 m²
- For underfloor heating screeds — minimum 65mm above top of heating pipe confirmed
✓Substrate Preparation+-
- Structural slab cleaned of all dust, laitance, oil, and curing compound before screed
- For bonded screed — slab surface mechanically prepared and bonding slurry applied
- For unbonded screed — DPM (250-micron polythene) laid flat, lapped 300mm, turned up at edges
- For floating screed — insulation boards flat, fully supported, joints staggered
- Perimeter isolation strips installed at all walls, columns, and fixed elements before screed
- All floor services (underfloor heating, conduits, pipes) installed and tested before screed
- Structural slab level surveyed — high and low points identified, screed thickness variation managed
- Structural slab moisture content confirmed below 75% RH before bonded or floating screed
✓Laying & Level Control+-
- Screed rails or dots set to correct finished screed level across full floor area
- Laser level or optical level used to confirm finished screed level at multiple points
- Semi-dry screed consistency correct — holds shape when squeezed in the fist without releasing free water
- Screed bays planned — maximum 40 m² per bay, or 8m maximum dimension
- Screed fully compacted — tamped or rolled to close voids before floating
- Power floating timed correctly — screed firm enough to support the machine without overworking
- Falls to floor drains confirmed and verified — minimum 1:80 fall toward drain
✓Curing & Protection+-
- Screed curing started within 24 hours — polythene sheet or damp hessian applied
- Screed cured for minimum 7 days — polythene or wet hessian maintained throughout
- No foot traffic for 24 hours; no point loads or stacked materials for 7 days
- Screed confirmed dry before floor finish is applied — minimum 1 day per mm thickness
- Screed inspected for cracking after curing — hairline cracks logged, wide cracks investigated
- Screed protected from damage during remaining construction — hardboard or plywood cover provided
✓Quality Checks & Defect Prevention+-
- Screed flatness checked with 3m straightedge — deviation within ±3mm for tiled floors
- Screed hollow test performed — tap entire screed systematically before floor finish
- Structural expansion joints in slab continued through screed — not bridged
Floor Screed Cement Consumption
In preliminary construction estimation, screed material quantities are often approximated using standard consumption values per mix ratio — useful for a quick sanity check before a detailed calculation. These figures are this calculator's own output before wastage.
| Screed Mix Ratio | Cement Bags per m³ | Sand Volume per m³ |
|---|---|---|
| 1 : 3 | ~9.6 bags | ~1.00 m³ |
| 1 : 4 | ~7.7 bags | ~1.06 m³ |
| 1 : 5 | ~6.4 bags | ~1.11 m³ |
For a practical per-square-metre reference at 1:4 mix: roughly 0.38 cement bags/m² at 50mm thickness, or 0.58 bags/m² at 75mm. Actual screed consumption may vary depending on floor surface conditions, compaction efficiency, and material handling losses.
Typical Wastage Guide by Work Type
| Work Type | Suggested Wastage % |
|---|---|
| Machine-mixed, mechanically screeded, large regular areas | 5% – 10% |
| Hand-mixed, hand-laid, irregular areas or many thresholds | 12% – 15% |
When should you use this floor screed calculator?
- Estimating cement and sand for floor leveling before tile or flooring installation.
- Planning material procurement for floating, bonded, or unbonded screed systems.
- Estimating screed for underfloor heating floor build-ups.
- Preparing cost estimates for flooring projects with the optional cost fields.
- Cross-checking a contractor's cement and sand claim against an independent estimate.
Quick Screed Estimation Tips
- Confirm screed thickness from the finishing schedule, not a guess — it's the gap between structural slab level and finished floor level, minus the floor finish thickness.
- Match minimum thickness to screed type: 38mm bonded, 50mm unbonded (on DPM), 65mm floating, 75mm over underfloor heating pipes.
- Use 1:4 for general flooring and 1:3 only where a specification calls for heavy-duty industrial strength — 1:5 is for light leveling only, not a load-bearing finish base.
- Increase wastage toward 15% for hand-laid, irregular rooms with many thresholds, and keep it at 5-10% for large, machine-screeded areas.
- Order cement in whole bags and round up — the result card already does this for you in the recommended quantity.
Common Mistakes
- Applying the concrete dry volume factor (1.54) instead of screed's (1.33), which overstates cement and sand by roughly 16%.
- Using less than the minimum thickness for the screed type — 38mm bonded, 50mm unbonded, 65-75mm floating/heated — risking cracking under load.
- Skipping wastage entirely for hand-mixed, hand-laid screed, where screed rails, dots, and trimming create real material loss.
- Tiling or laying flooring over screed that hasn't fully dried — screed needs roughly 1 day per mm thickness to dry, not just cure.
- Forgetting to build in falls toward floor drains in wet areas, relying instead on the structural slab to have the correct fall.
Limitations
- Estimates one uniform thickness over one rectangular area — does not model a floor with a slope/fall or varying thickness from an uneven slab.
- Does not deduct columns, staircases, or fixed elements from floor area — enter net screed area if these are significant.
- Assumes a standard cement:sand mix — proprietary anhydrite/calcium sulphate liquid screed uses different materials and is not modeled.
- Cost excludes labour, mixing, and laying — material cost only.
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.