How Much Concrete for an 8x10 Slab?
Concrete needed
1.09 cubic yards
An 8 by 10 foot slab at four 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.
- Length8 ft
- Width10 ft
- Thickness4 in
- Waste allowance10 %
Concrete needed1.09 cubic yards
| Volume | 26.7 cu ft |
|---|---|
| Cubic yards before waste | 0.99 |
| Cubic yards with 10% waste | 1.09order to this number |
| Order in quarter yards | 1.25 cu yd |
| 60 lb bags, if bagging it | 66 |
| 80 lb bags, if bagging it | 49 |
The material list this produces
| Ready mix concrete, cubic yards | 1.25 |
|---|---|
| Rebar or mesh, sq ft of slab | 80 |
| Form lumber, linear ft | 36 |
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 | 1.09 cubic yards |
| 5 in | 1.36 cubic yards |
| 6 in | 1.63 cubic yards |
| 8 in | 2.17 cubic yards |
What else matters here
Eighty square feet is the classic small shed pad, and it sits right on the line between bagging it and ordering it. It is about a yard, which is the minimum load for most suppliers, so for the first time the truck is genuinely competitive.
If you do bag it, the count is high enough that the mix has to be continuous. Set the forms, have every bag open and every tool laid out, and start at the far corner. A pad this size done in two sessions has a seam through the middle of it whether you can see it or not.
A shed pad usually wants a thickened edge rather than a uniform four inches. Digging the perimeter down to eight or ten inches for a foot in from the form adds a small amount of concrete and gives the walls something to sit on. The calculator figures the flat slab, so add that trench volume separately.
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 bags of concrete for an 8x10 slab?
About 66 sixty pound bags or 49 eighty pound bags at four inches thick with waste included. That is a long morning of mixing, which is why this size is where most people switch to ready mix.
How thick should a shed slab be?
Four inches for a garden or storage shed. Six if you will park a mower, a quad or a small tractor on it, or if the shed is a workshop with a bench and machinery.
Do I need rebar in an 8x10 slab?
Wire mesh or a light rebar grid is cheap insurance on any slab this size. It does not stop concrete cracking, it holds the two sides of a crack together so the slab stays one piece and stays level.
The concrete calculator takes any dimensions you like and hands back the same list.