TryBuildCalcM20 Concrete Material Calculator (1:1.5:3 Mix Ratio)
Estimate M20 concrete materials instantly.
🕒 Last updated: August 17, 2026
Inputs
Cost
For a 9.00 m² footprint (M20, 1:1.5:3), you need approximately 1.42 m³ (50.1 cft) of concrete — 12 cement bags.
Concrete Volume
Wet volume (before wastage): 1.350 m³
Dry volume: 2.079 m³
Final quantity (with wastage): 1.42 m³ (50.1 cft)
Materials
Cement: 11.4 bags (572 kg) — buy 12 bags
Sand: 0.60 m³ (21.0 cft)
Aggregate: 1.19 m³ (42.1 cft)
Water (approx., w/c 0.50): 286 litres
Order Summary — Theoretical vs. Order Quantity
| Material | Theoretical | Order Quantity |
|---|---|---|
| Concrete | 1.35 m³ | 1.42 m³ (50.1 cft) |
| Cement | 10.9 bags | 12 bags (whole) |
| Sand | 0.57 m³ | 0.60 m³ |
| Aggregate | 1.13 m³ | 1.19 m³ |
| Water (approx.) | 272 litres | 286 litres |
Theoretical = before wastage. Order Quantity = after your 5.0% wastage allowance (cement rounded up to a whole bag).
Assumptions Used
Dry volume factor: 1.54 | Cement bag: 50 kg / 0.0347 m³ | Nominal mix ratio (not a lab-designed mix) | Water quantity uses a typical water-cement ratio for this mix — approximate, and not a substitute for a lab-verified mix design | Wastage applied once to the final wet volume, cement, sand, and aggregate figures.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Concrete Cement Calculator.
M20 concrete (1:1.5:3) material estimate
M20 is the minimum grade commonly used for reinforced concrete (RCC) work — this page is pre-selected to the 1:1.5:3 nominal mix, so the result shows the cement, sand, and aggregate for M20 concrete directly.
Edit the dimensions above and the material breakdown and worked example update from the active values, still using the M20 mix ratio.
- M20 (1:1.5:3) typically requires about 8 cement bags per cubic metre.
- Commonly used for RCC slabs, beams, columns, and general structural work.
- Dry volume correction (×1.54) is applied before the mix ratio split.
Concrete Cement Formula: How Is Quantity Calculated?
Understanding how cement quantity is calculated helps in verifying estimates and improving construction material planning accuracy.
Step 1 — Concrete Volume
Wet Volume = Length × Width × Thickness
Dry Volume = Wet Volume × 1.54
Wet volume is the poured volume for slabs, footings, beams, or columns. Dry volume accounts for voids between aggregate particles, bulking of sand, and practical construction losses that disappear once the concrete is mixed and compacted.
Step 2 — Mix Ratio Distribution
Cement Volume = Dry Volume × (Cement Part ÷ Total Parts)
Sand Volume = Dry Volume × (Sand Part ÷ Total Parts)
Aggregate Volume = Dry Volume × (Aggregate Part ÷ Total Parts)
Dry volume is distributed according to the selected mix ratio — for example 1:1.5:3 (M20) or 1:2:4 (M15). Total Parts is the sum of all three ratio parts.
Step 3 — Cement Quantity Conversion
Cement Bags = Cement Volume ÷ 0.0347 m³/bag (50 kg bags)
One standard cement bag (50 kg) occupies approximately 0.0347 cubic meters. This conversion translates calculated cement volume into practical material procurement quantities.
Step 4 — Final Quantity with Wastage
Final Wet Volume = Wet Volume × (1 + Wastage %)
This final wet volume (and the wastage-adjusted cement, sand, and aggregate figures) is the practical quantity to order or batch on site — shown separately from the theoretical pre-wastage volume.
Step 5 — Approximate Mixing Water
Final Cement Weight = Final (Wastage-Adjusted) Cement Bags × 50 kg
Water (litres) = Final Cement Weight × Water-Cement Ratio
Mixing water is estimated from the final, wastage-adjusted cement quantity above — not the pre-wastage figure — using a typical water-cement ratio for the selected nominal mix (roughly 0.45 for M25 down to 0.60 for M5, since 1 litre of water weighs about 1 kg). This is a planning estimate only — actual water-cement ratio depends on aggregate moisture, workability needs, and (above M20) the project's lab-verified mix design.
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 × thickness | 3m × 3m × 0.15m | Sets the wet concrete volume |
| Mix ratio / wastage | 1:1.5:3 (M20), 5% wastage | Splits dry volume into cement/sand/aggregate and adds a buffer for site losses |
Step 1 — Volume
| Calculation | Substitution | Result |
|---|---|---|
| Wet volume | 3m × 3m × 0.15m | 1.350 m³ |
| Dry volume | 1.350 × 1.54 | 2.079 m³ |
| With 5% wastage | 1.350 × 1.05 | 1.417 m³ (50.1 cft) |
Step 2 — Materials
| Material | Quantity |
|---|---|
| Cement | 11.4 bags (572 kg) — buy 12 bags |
| Sand | 0.60 m³ (21.0 cft) |
| Aggregate | 1.19 m³ (42.1 cft) |
| Water (approx.) | 572 kg × 0.50 w/c = 286 litres |
Therefore, approximately 1.42 m³ (50.1 cft) of concrete should be ordered or batched for this element, needing 12 cement bags.
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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.