Work out the concrete volume for a rectangular slab and carry a separate waste allowance into the order quantity. Enter slab length, width, and thickness in feet and inches; the calculator converts thickness to feet before multiplying. Results are shown in cubic yards and cubic feet, plus the added allowance, so the takeoff can be checked before requesting a supplier quote.
The order volume is geometric slab volume plus the allowance you selected.
Thickened edges, grade beams, penetrations, and uneven subgrade require separate adjustments.
A 30 ft × 20 ft slab at 4 in thick contains 200 ft³, or 7.41 yd³. Adding 5% gives 7.78 yd³.
Usually not. Field variation and handling loss can justify a separate allowance, which this calculator displays explicitly.
Convert every dimension to the unit shown by the field before calculating.
No. The result covers concrete volume unless an input or output explicitly says otherwise.
They often have different dimensions, placement conditions, and waste assumptions.
No. Confirm dimensions, specifications, and order increments with the project documents and supplier.
| Item | How it is used |
|---|---|
| Net volume | Calculator input in the displayed unit |
| Allowance volume | Calculator input in the displayed unit |
| Order volume in cubic feet | Calculator input in the displayed unit |