Quick answer
A 10×10 slab at 4 inches thick contains about 1.23 cubic yards of concrete before waste. In practice, ordering a modest buffer is common because subgrade variation, forms and placement losses can increase the actual volume needed.
How to work it out
- Convert slab thickness from inches to feet.
- Multiply length × width × thickness for cubic feet.
- Divide cubic feet by 27 for cubic yards.
- Add your chosen waste/contingency allowance.
- Round the order based on the supplier’s increment and minimums.
Example
10 ft × 10 ft × 0.333 ft is about 33.3 cubic ft. Divide by 27 and the theoretical volume is about 1.23 yd³. A 10% allowance brings that to roughly 1.36 yd³.
What can change the answer
Do not use a simple volume estimate as a structural design. Thickness, reinforcement, base preparation and local requirements are separate decisions.
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