Concrete & gravel cubic-yard conversions

A cubic yard is 27 cubic feet, so concrete or gravel volume = area (sq ft) × thickness (ft) ÷ 27, and thickness in inches is divided by 12 first. That is a fixed convention, not a price. The table shows cubic yards for common slab sizes; add your own $/cu yd in the slab, footing and French drain tools.

AreaThicknessConcrete (cu yd)
100 sq ft4 in1.23 cu yd
200 sq ft4 in2.47 cu yd
400 sq ft4 in4.94 cu yd
400 sq ft6 in7.41 cu yd
600 sq ft4 in7.41 cu yd

27 cubic feet = 1 cubic yard; cu yd = area × (thickness in ÷ 12) ÷ 27. Order a little extra for spillage and uneven subgrade.

Concrete by slab area and thicknessHorizontal bars comparing the cubic yards of concrete needed for the slab sizes in the table above, scaled from zero.100 sq ft at 4 in1.23 cu yd200 sq ft at 4 in2.47 cu yd400 sq ft at 4 in4.94 cu yd400 sq ft at 6 in7.41 cu yd600 sq ft at 4 in7.41 cu ydcu yd = area × (thickness in ÷ 12) ÷ 27
Thickness moves the volume as hard as area does: half again the depth is half again the concrete. 400 sq ft at 6 in and 600 sq ft at 4 in take the same pour. Order a little extra for spillage and uneven subgrade.

Related calculators

Concrete Slab CostCalculate concrete slab cost: cubic yards from area and thickness, times your $/cu yd, plus your labor per square foot. A planning estimate on your own numbers.Footing CostCalculate concrete footing cost: cubic yards from length, width and depth, times your price per cubic yard. A planning estimate on your own numbers.French Drain CostEstimate French drain cost from trench length and your price per foot, plus the gravel cubic yards and perforated pipe the trench needs. Free, no signup.