Concrete Calculator

How to work out how much concrete you need

1. Choose a slab or footing, or a round column, and meters or feet.
2. Enter the dimensions and how many you need.
3. Keep 10% extra for waste or change it, and read the volume and number of bags.

Frequently asked questions

How many bags make a cubic yard?

About 45 bags of 80 lb or 60 bags of 60 lb. An 80 lb bag makes about 0.6 ft³ of concrete.

How is the volume worked out?

Length × width × depth for a slab, or π × radius² × height for a round column, times the number of pieces, plus the waste allowance.

Why order extra?

Uneven ground, spills and forms that bow outward all use more concrete than the plans show. 5 to 10% extra is usual.