How Much Concrete for a 24x24 Garage Slab?
Concrete needed
11.73 cubic yards
A 24 by 24 foot garage slab at six inches, with ten percent on top for waste.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Length24 ft
- Width24 ft
- Thickness6 in
- Waste allowance10 %
Concrete needed11.73 cubic yards
| Volume | 288 cu ft |
|---|---|
| Cubic yards before waste | 10.67 |
| Cubic yards with 10% waste | 11.73order to this number |
| Order in quarter yards | 11.75 cu yd |
| 60 lb bags, if bagging it | 704 |
| 80 lb bags, if bagging it | 528 |
The material list this produces
| Ready mix concrete, cubic yards | 11.75 |
|---|---|
| Rebar or mesh, sq ft of slab | 576 |
| Form lumber, linear ft | 96 |
Thickness compared
Thickness is the one number on this page worth arguing about, so here is the same slab at each of the usual four.
| Thickness | Concrete needed |
|---|---|
| 4 in | 7.82 cubic yards |
| 5 in | 9.78 cubic yards |
| 6 in | 11.73 cubic yards |
| 8 in | 15.64 cubic yards |
What else matters here
Twenty four by twenty four is the standard two car detached garage, and this page runs it at six inches rather than four because that is what a floor carrying two vehicles should be. At six inches with waste it is nearly twelve yards, which is two trucks or one large one.
Two trucks means a cold joint risk. Order them back to back, tell the dispatcher they are for one continuous pour, and have the second one arriving as the first is finishing rather than an hour later. If there is any doubt, pour the slab in defined halves with a proper construction joint and keyway rather than pretending it went in as one.
A garage slab also wants a thickened perimeter footing unless the walls sit on a separate foundation, and it wants the apron at the door thickened and reinforced. The calculator gives the flat slab volume, so figure those trenches separately and add them to the order.
What this calculator assumes
- One cubic yard is 27 cubic feet. A 4 inch slab is one third of a foot thick, not 4.
- A 60 lb bag yields about 0.45 cubic feet and an 80 lb bag about 0.60. Bags are for small pours only; past about one cubic yard, ready mix is cheaper and far less work.
- Ready mix is usually sold in quarter yard steps with a short load fee below one yard.
Questions people ask
How many yards of concrete for a 24x24 garage?
10.67 cubic yards at six inches, 11.73 with a ten percent waste allowance. At four inches the same floor is 7.8 yards, but four inches is thin for two vehicles.
Should a garage floor be 4 or 6 inches?
Six for a garage that vehicles drive into, four only for storage. The extra two inches is roughly four extra yards on this size, which is far cheaper than cutting out a cracked bay later.
What rebar goes in a 24x24 garage slab?
Number four bar on a grid, commonly 18 inches on center for a residential garage, chaired up so it sits in the middle third of the slab depth. Mesh lying on the ground does nothing at all.
The concrete calculator takes any dimensions you like and hands back the same list.