Estimate how much concrete you need for a slab, footing or patio. Enter the length, width and thickness, and see the volume in cubic yards, cubic feet and cubic metres, plus the number of 80 lb bags.
| Cubic feet | – |
| Cubic yards | – |
| Cubic metres | – |
| 80 lb bags (about 0.6 cu ft each) | – |
How it works
Volume = length × width × thickness. The calculator converts everything to cubic metres, adds your waste allowance, and then converts to cubic feet (× 35.3147) and cubic yards (× 1.30795). A standard 80 lb bag of pre-mixed concrete yields about 0.6 cubic feet. Ready-mix is sold by the cubic yard or cubic metre.
Slopes, thicker edges and uneven ground use more concrete. Ask your supplier for advice on large or structural jobs.
Example
A 10 ft by 10 ft slab that is 4 inches thick is 33.3 cubic feet, or 1.23 cubic yards. With 10% waste, about 1.36 cubic yards, or 62 bags of 80 lb mix.
Frequently asked questions
How thick should a concrete slab be?
Many patios and walkways are about 4 inches (10 cm). Driveways and heavy loads need more. Check local guidance.
How many bags make a cubic yard?
About 45 bags of 80 lb mix, because one bag yields around 0.6 cubic feet and a cubic yard is 27 cubic feet.
Should I order extra?
Yes. Around 5 to 10 percent extra is common.
More free tools: Area calculator · Unit converter · All free tools
Estimates only. Always check product instructions and add a safety margin before you buy materials. Structural work should follow professional advice.