Concrete Mix Calculator

How it works

1. 1Enter the wet concrete volume you need to pour (m³ or yd³).
2. 2Select a standard mix ratio — 1:2:4 general, 1:1.5:3 structural, or 1:3:6 lean fills and footings.
3. 3The calculator applies a 1.54 dry/wet factor, then splits the dry volume by the ratio into cement bags, sand, and gravel.

Use cases

• Estimating cement bags for a house slab or driveway before ordering from a supplier.
• Comparing material quantities between C20 and C25 mix designs for a structural element.
• Planning aggregate deliveries for a site with multiple small pours in a day.

Frequently asked questions

Why multiply by 1.54 to get the dry volume?

Dry aggregates contain air voids that fill in when mixed with water and cement, so the total volume shrinks by roughly 35–40%. Multiplying wet volume by 1.54 ensures you order enough dry material to reach the target poured volume.

How many bags of cement does 1 m³ of 1:2:4 concrete need?

Dry volume = 1 × 1.54 = 1.54 m³. Cement share = 1.54 × (1 ÷ 7) ≈ 0.22 m³. At 1440 kg/m³ that is ≈ 317 kg → 7 bags of 50 kg.

What densities are used for sand and gravel?

The calculator uses 1600 kg/m³ for sand and 1680 kg/m³ for gravel — typical bulk densities for construction aggregates. Your supplier material may differ slightly, so treat results as planning estimates.