Concrete calculator
How much concrete you need for a slab, footing or wall, in cubic yards and in 40, 50, 60 or 80 lb bags.
You need about
1.36 cubic yards
- Cubic feet
- 36.7
- 80 lb bags
- 62
- 60 lb bags
- 82
- 50 lb bags
- 98
- 40 lb bags
- 123
- Weight (typical)
- 5,317 lb (2.66 tons)
- Cubic meters
- 1.04
- Estimated cost
Bags from the yields printed on standard concrete mix (e.g. an 80 lb bag makes about 0.60 cu ft); high-yield mixes make more, so check the bag. Weight can run 5,133 to 5,500 lb depending on the mix.
How to figure yards of concrete
Concrete is ordered by volume. Multiply the length, width and thickness in feet, divide by 27 to get cubic yards, and add a little extra for spills, a low spot in the ground or forms that bow out.
- Cubic feet = length (ft) × width (ft) × thickness (in) ÷ 12. For a footing, the width and depth are in inches, so divide each by 12. For a wall, use the height in feet in place of the width.
- With extra = cubic feet × (1 + extra ÷ 100), times the number of identical pieces
- Cubic yards = cubic feet ÷ 27
- Bags = cubic feet ÷ the bag's yield, rounded up
- Weight = cubic feet × 145 lb (typical normal-weight concrete)
Worked example
A 10 × 10 ft slab, 4 inches thick: 10 × 10 × 4 ÷ 12 = 33.33 cubic feet, and 33.33 ÷ 27 = 1.23 cubic yards. In 80 lb bags at 0.60 cu ft each, that's 33.33 ÷ 0.60 = 55.6, so 56 bags (or 75 bags of 60 lb). It weighs about 4,833 lb. Add the extra percentage you enter above before you order.
Bags of concrete per cubic yard
Yields from the QUIKRETE Concrete Mix (No. 1101) data sheet, revised October 2022. A cubic yard is 27 cubic feet.
| Bag | Yield per bag | Bags per cubic yard |
|---|---|---|
| 80 lb | 0.600 cu ft | 45 |
| 60 lb | 0.450 cu ft | 60 |
| 50 lb | 0.375 cu ft | 72 |
| 40 lb | 0.300 cu ft | 90 |
Concrete for a 10 × 10 ft slab by thickness
No extra added. Weight at a typical 145 lb per cubic foot.
| Thickness | Cubic yards | 80 lb bags | 60 lb bags | Weight |
|---|---|---|---|---|
| 3 in | 0.93 | 42 | 56 | 3,625 lb |
| 4 in | 1.23 | 56 | 75 | 4,833 lb |
| 5 in | 1.54 | 70 | 93 | 6,042 lb |
| 6 in | 1.85 | 84 | 112 | 7,250 lb |
| 8 in | 2.47 | 112 | 149 | 9,667 lb |
Concrete questions
How many bags of concrete are in a yard?
About 45 bags of 80 lb, 60 bags of 60 lb or 90 bags of 40 lb, using the yields printed on standard concrete mix. High-yield or lightweight mixes make more per bag, so use the yield on your bag.
How much does a yard of concrete weigh?
About 3,915 lb, or about 2.0 tons. Normal-weight concrete runs 140 to 150 lb per cubic foot (Iowa DOT Materials IM 340, Weight per Cubic Foot, Yield & Air Content (Gravimetric) of Concrete), so a yard weighs 3,780 to 4,050 lb.
How much concrete do I need for a 10 × 10 slab?
At 4 inches thick, 1.23 cubic yards: 56 bags of 80 lb. The table above gives other thicknesses; enter your own size above for anything else.
Should I use bags or order ready-mix?
Bags suit small jobs you can mix by hand or in a rented mixer: posts, pads, steps and small slabs. For bigger pours a ready-mix truck saves a lot of mixing, and the concrete is placed all at once. Ask your supplier about minimum orders and short-load charges, and enter their price per yard above to compare it with the bag cost.
How much extra concrete should I order?
The calculator adds the percentage you enter. Order more when the ground is uneven or the forms are long, because running short mid-pour leaves a weak joint. For structural footings and walls, follow the plans and local code and talk to a qualified professional.