How to measure
Measure the slab length, width and specified thickness. Use the yield on the exact bag you will purchase.
How the estimate works
Length × width × thickness ÷ 12 gives cubic feet. Add allowance; divide by bag yield and round up.
A worked example
A 10 × 8 ft slab at 4 in thick needs 26.67 cubic feet. With 10% allowance and 0.6 cubic feet per bag, buy 49 bags.
Before you buy
Quantity estimate only, not a structural design. Reinforcement, foundations, permits and load requirements need qualified advice. Default values are illustrative starting points. Check the label and adjust them to your product.