Concrete Calculator
Estimate concrete volume, cubic yards, and bags needed for a slab, footing, or column.
A typical slab-on-grade is about 10–15 cm thick; a footing is usually thicker.
Industry guidance typically recommends adding 5–10% for spillage, uneven subgrade, and mixing loss.
Enter your values to calculate your result.
Formula
Volume = Length × Width × Thickness × (1 + Waste %)
Length and Width are in meters, Thickness is converted from centimeters to meters before multiplying. The result is the raw rectangular volume, then increased by the waste/overage percentage to get the total volume to order. Bags Required is that total volume divided by the selected bag's published yield, rounded up to a whole bag.
Example
A 5 m × 4 m slab at 10 cm thick has a base volume of 2.0 m³. Adding a 10% waste allowance brings the total to 2.2 m³ (about 2.88 cubic yards) — roughly 183 bags of 25 kg premix, or 130 bags of 80 lb premix.
Frequently Asked Questions
Why add a waste/overage percentage?
Real pours always lose some material to spillage, an uneven subgrade, or over-excavation. Adding 5–10% on top of the exact geometric volume is standard practice so you don't run short mid-pour.
Does this account for reinforcement (rebar or mesh)?
No — this calculates the concrete volume only. Steel reinforcement is a separate material estimate based on your specific structural plan.