Calculator + chartEnter your measurements below and it works the answer out.
A cubic yard of concrete covers 81 sq ft at 4 in deep. Enter your area and depth for the volume, the weight range and the bag count, with 10% waste added.
| Depth | Square feet covered | Square feet per cubic foot |
|---|---|---|
| 1 in | 324 sq ft | 12 sq ft |
| 2 in | 162 sq ft | 6 sq ft |
| 3 in | 108 sq ft | 4 sq ft |
| 4 in | 81 sq ft | 3 sq ft |
| 5 in | 64.8 sq ft | 2.4 sq ft |
| 6 in | 54 sq ft | 2 sq ft |
| 8 in | 40.5 sq ft | 1.5 sq ft |
| 12 in | 27 sq ft | 1 sq ft |
Every figure here is 324 ÷ depth in inches, because a cubic yard is 27 cubic feet and one square foot at D inches deep is D/12 of a cubic foot. Nothing on this site uses a coverage number that does not come out of that line.
cubic yards = length × width × (depth ÷ 12) ÷ 27Depth is the only measurement in inches, so it is divided by 12 to put it in feet. Dividing by 27 turns cubic feet into cubic yards, because a cubic yard is 27 cubic feet — that is a definition, not an estimate. The calculator then adds 10% for waste.
Say a 20 ft by 12 ft area, 4 in deep.
Area. 20 × 12 = 240 sq ft.
Volume. 240 × (4 ÷ 12) = 80 cubic feet.
Cubic yards. 80 ÷ 27 = 2.96 cubic yards.
With 10% waste. 2.96 × 1.1 = 3.26 cubic yards to order.
The rule. A cubic yard is 27 cubic feet. Spread D inches deep it covers 324 ÷ D square feet — so a cubic yard of concrete 4 in deep covers 81 sq ft, 5 in deep covers 64.8 sq ft, 6 in deep covers 54 sq ft. Multiply your area by the depth in feet, divide by 27, and that is your order in cubic yards. Everything else on this page is that line with the units changed.
Depth is the decision, not the area. A 4 in slab is the normal thickness for a patio, shed base or walkway. Driveways that take vehicles go to 5 or 6 in, and thickness matters far more than strength grade for whether a slab cracks.
How it is sold. Ready-mix is ordered in cubic yards, usually with a one-yard minimum and a short-load fee under about three yards. Bagged mix makes sense up to roughly half a yard; past that the bags cost more than the truck.
Weight is a range, and deliberately so. Concrete runs about 1.9 to 2.1 tons per cubic yard. That is a real spread, not sloppiness: bulk material weighs more wet than dry, and more when it is fine than when it is coarse. Order by volume, and use the tonnage only to check that a delivery ticket is in the right country.
Waste. This calculator adds 10%. Ground is never as flat as a tape says it is, edges are never square, and running out halfway through means a second delivery charge for a fraction of a load. 10% is the allowance that stops that without leaving a pile you have to get rid of.
Multiply the area in square feet by the depth in feet, then divide by 27 for cubic yards. A 10 by 12 ft area at 4 in is 1.48 cubic yards before waste. The calculator above does it and adds the 10% allowance.
At 4 in it covers 81 sq ft. At 5 in it covers 64.8 sq ft. At 6 in it covers 54 sq ft. The figure is always 324 divided by the depth in inches.
About 1.9 to 2.1 tons per cubic yard. The range is real — moisture and grading move it — so treat the middle of it as an estimate and never as a delivery spec.
A cubic yard is 27 cubic feet. At the common published yields that is 45 bags at 80 lb, 60 bags at 60 lb, or 90 bags at 40 lb. That is also the point where bagged mix stops making sense — a yard of ready-mix is usually cheaper than 45 bags and very much less work.
Four inches for a patio, shed floor or footpath. Five to six inches where a car or a trailer will sit on it. Thickness does more for crack resistance than mix strength does, and going from 4 in to 6 in adds 50% to the volume — which is exactly what this calculator will show you.
By the yard wherever the supplier allows it. Volume is what your project consumes; weight is what the truck carries, and the same yard weighs differently in July and in November. Where a yard only sells by weight, use the range above to convert and round up.
Free to use on any site, including commercial ones. Paste this where you want it to appear — it keeps working when we update the figures.