Formula used
Cubic yards = [length × width × (thickness ÷ 12) ÷ 27] × (1 + waste ÷ 100)
Worked concrete slab example
Concrete Slab Calculator example: 15.4 ft × 14.4 ft × 4 in ÷ 12 ÷ 27 × 1.1 = 3.01 yd³. The same volume is about 137 80-lb premixed-concrete bags or 181 60-lb bags using the calculator's bag-yield constants.
From calculated volume to an order
Compare the calculated yardage with the supplier's minimum-load and short-load policies, and calculate isolated thickened edges as separate shapes when necessary.
Where a concrete takeoff can drift
A crowned subbase, edge thickening, depressions, beams, and floor drains make a slab consume more or less concrete than a uniform prism.
Questions specific to this calculation
Which finished dimensions define the concrete slab placement?
Enter the slab's inside form length and width, then use the specified concrete thickness rather than the excavation depth below the forms.