How this calculator works
All dimensions use the selected unit, including depth. This measures volume only: it does not design reinforcement, specify concrete strength or account for uneven excavation. Confirm delivery increments and actual site dimensions with your supplier.
The formula
Net volume = length × width × depth, converted to meters. Order volume = net volume × (1 + allowance/100).A quick example
A 5 m × 4 m slab at 0.1 m depth contains 2 m³. A 10% allowance brings the estimate to 2.2 m³.
How to use this calculator
- Choose the settings that match your scenario, using the units shown beside each field.
- Enter slab length, slab width, slab depth, waste allowance (%).
- Calculate, then review the method and assumptions alongside the results.
A few common questions
Can I enter depth in centimeters while other dimensions are meters?
Convert depth first or select a common unit for all three fields. For example, 10 cm is 0.1 m.
Does this estimate bags of dry concrete?
No. Bag yield differs by product. Divide the order volume by the manufacturer’s mixed-volume yield.