Concrete Volume Calculator

How it works

1. 1Enter the slab length and width in metres (or feet) and the thickness in centimetres (or inches).
2. 2Set a waste allowance percentage — typically 5–10% — to account for spillage and uneven subgrade.
3. 3Read off the total concrete volume and estimated weight, ready to share with your supplier.

Use cases

• Estimating how many cubic metres or cubic yards of ready-mix to order for a driveway or patio slab.
• Checking delivery quantities before placing a concrete order to avoid shortfalls or excess.
• Budgeting material costs for footings, floor slabs, or garden paths on a construction project.

Frequently asked questions

How is the concrete volume calculated?

Volume = Length × Width × Thickness × (1 + waste ÷ 100). For example, a 5 m × 4 m slab at 10 cm thick with 5% waste gives 5 × 4 × 0.10 × 1.05 = 2.10 m³.

Why is a waste allowance recommended?

Volume calculations assume a perfectly flat subgrade. In practice, ground undulation, formwork gaps, and over-pour typically consume an extra 5–10%, so ordering a little extra avoids a costly second delivery.

How much does concrete weigh per cubic metre?

Standard ready-mix concrete is about 2,400 kg/m³ (2.4 t/m³, roughly 150 lb/ft³). This calculator uses that density to estimate the total mass for planning lifts or checking ground-bearing capacity.