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Concrete slab calculator
Estimate the concrete volume for a rectangular slab from its length, width, and thickness. See cubic feet, cubic yards, cubic metres, and an approximate 80 lb bag count.
Slab dimensions
Enter your slab measurements in feet and inches, then calculate a planning quantity.
Estimated material volume
Includes your extra allowance. Results are approximate.
A 10 × 12 ft slab at 4 in thickness takes about 1.56 cubic yards including 5% allowance.
How this concrete estimate works
Convert slab thickness from inches to feet, then multiply length × width × thickness to calculate cubic feet. Divide by 27 to convert cubic feet to cubic yards. The optional extra allowance is added after the slab volume is calculated.
- Dimensions: Measure the actual pour area and planned depth, not just the formwork outside dimensions.
- Bagged concrete: Divide your total cubic feet by the bag's stated cured yield; different mixes and bag sizes vary.
- Ready-mix concrete: Confirm minimum delivery quantities, site access, overage, and ordering rules with your supplier.
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Before you order
This estimate covers nominal rectangular slab volume only. It does not include thickened edges, additional footings, uneven excavation, spillage, compaction, reinforcing material, or labor. For irregular pours, divide the area into measurable sections and check each separately.
For more detailed options, use the complete EstimatorPad concrete calculator.