Concrete Calculator
Enter your slab or footing dimensions and get real cubic yards, plus bag counts if you're buying bagged mix.
You'll need
1.23 cubic yards
(33.3 cubic feet)
80lb bags needed
56 bags
Standard trade advice is to order 5-10% extra to cover spillage, form variance, and subgrade irregularity -- running short mid-pour is a much bigger problem than a little leftover mix.
Keep going
- Footings are also poured concrete, just in narrow strip or pier forms; the footing calculator handles that shape instead of a flat slab. Footing Calculator
- Slabs over about 4 inches typically need reinforcement; the rebar calculator sizes the grid of bar for your dimensions. Rebar Calculator
Frequently Asked Questions
How much concrete do I need for a 10x10 slab?
At the common 4" slab thickness, a 10x10 ft area needs about 1.23 cubic yards -- plug your own dimensions into the calculator above since thickness changes the number a lot (a 6" slab for the same area needs about 1.85 cubic yards).
Should I order ready-mix or use bags?
Ready-mix (ordered by the cubic yard from a concrete truck) is usually cheaper past about 1 cubic yard and pours faster. Bagged concrete makes more sense for small pours (footings, post holes, patch repairs) where a truck minimum wouldn't be worth it.
Why do bag counts round up?
You can't buy a fraction of a bag, and running short mid-pour is a real problem, so the bag count here always rounds up to the next whole bag rather than down.