Concrete Calculator
Work out cubic yards for a ready-mix delivery, or how many bags to carry home, for slabs, footings and post holes.
What are you pouring?
The shape decides which measurements matter.
How are you buying it?
Bagged for small pours, ready-mix once you pass about a cubic yard.
Common questions
How much concrete do I need for a 10x10 slab?
At 4 inches thick, a 10 by 10 foot slab needs 33.3 cubic feet, which is 1.24 cubic yards, or 56 bags at 80 lb. At 5 inches it rises to 1.54 cubic yards. Order a little over rather than under: a short pour that sets before the second load arrives leaves a cold joint.
How many 80 lb bags of concrete make a cubic yard?
45. An 80 lb bag yields about 0.6 cubic feet, and there are 27 cubic feet in a yard. That is 60 bags at 60 lb, or 90 bags at 40 lb. Once you are mixing more than about 20 bags, ready-mix is usually cheaper and far less work.
How thick should a concrete driveway be?
Four inches is the usual minimum for cars, and 5 to 6 inches if trucks or an RV will park on it. Thickness is only half the job. A compacted base and control joints cut within the first day matter as much, because concrete cracks where you do not tell it to.
Write the numbers down
The free Backyard Project Planner has a materials table and an order of work to drop this estimate into.