TryBuildCalc75mm Screed Calculator (Floating / Underfloor Heating Screed)
Estimate materials for 75mm screed.
🕒 Last updated: August 23, 2026
Inputs
ℹ️Typical: 38-50 mm (bonded/unbonded), 65-75 mm (floating/underfloor heating)
Cost
For 9.00 m² of floor area, you need approximately 6 cement bags and 0.75 m³ of sand.
Screed Volume
Floor area: 9.00 m²
Wet volume: 0.675 m³
Dry volume (×1.33): 0.898 m³
Materials
Cement: 5.4 bags — buy 6 bags
Sand: 0.754 m³ (~1.21 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 | 5.2 bags | 6 bags (whole) |
| Sand | 0.718 m³ | 0.754 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 →
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Floor Screed Calculator.
75mm screed material estimate
75mm is the typical minimum thickness for floating screed over underfloor heating pipes — this page is pre-selected to that thickness with the standard 1:4 mix.
Edit the floor dimensions or mix ratio above and the material breakdown and worked example update from the active values, still using 75mm thickness.
- 75mm typically needs about 0.58 cement bags per m² at a 1:4 mix — significantly more than a 50mm layer.
- Standard minimum for screed laid over underfloor heating pipes (measured above the top of the pipe, not the insulation).
- Also suits floating screed over rigid insulation without heating pipes (65mm minimum).
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 | 3m × 3m | Sets the floor area to be screeded |
| Thickness / mix ratio / wastage | 75mm, 1:4, 5% wastage | Sets wet volume and splits dry volume into cement/sand |
Step 1 — Area & Volume
| Calculation | Substitution | Result |
|---|---|---|
| Floor area | 3m × 3m | 9.00 m² |
| Wet volume | 9.00 × 75mm | 0.675 m³ |
| Dry volume | 0.675 × 1.33 | 0.898 m³ |
Step 2 — Cement & Sand
| Material | Theoretical | Order Quantity |
|---|---|---|
| Cement | 5.2 bags | 6 bags (whole) |
| Sand | 0.718 m³ | 0.754 m³ |
Therefore, for 9.00 m² of floor at 75mm screed thickness and a 1:4 mix, you need approximately 6 cement bags and 0.75 m³ of sand.
Related Calculators
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.