How Much Concrete for a 6x8 Shed Pad?
Concrete needed
0.65 cubic yards
A 6 by 8 foot shed pad 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.
- Length6 ft
- Width8 ft
- Thickness4 in
- Waste allowance10 %
Concrete needed0.65 cubic yards
| Volume | 16 cu ft |
|---|---|
| Cubic yards before waste | 0.59 |
| Cubic yards with 10% waste | 0.65order to this number |
| Order in quarter yards | 0.75 cu yd |
| 60 lb bags, if bagging it | 40 |
| 80 lb bags, if bagging it | 30 |
The material list this produces
| Ready mix concrete, cubic yards | 0.75 |
|---|---|
| Rebar or mesh, sq ft of slab | 48 |
| Form lumber, linear ft | 28 |
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 | 0.65 cubic yards |
| 5 in | 0.81 cubic yards |
| 6 in | 0.98 cubic yards |
| 8 in | 1.3 cubic yards |
What else matters here
Six by eight is one of the most common shed kit footprints, and the slab is usually poured to the shed size exactly so the walls sit flush with the edge. Pouring it a couple of inches larger is a mistake that shows: rain lands on the ledge and runs back under the wall plate.
Frost is the question that decides how this is built. In a climate with real frost, a slab sitting on grade will move with the ground, and for a shed that is normally accepted rather than fought, because a shed can move a little without harm. If it must not move, the edge has to be thickened down below the frost line or set on footings, which is a different and much larger pour.
Whatever is decided, get the gravel right. Four to six inches of compacted crushed stone, not sand and not the soil that came out, and compact it in layers rather than in one go.
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 a 6x8 shed pad?
About 40 sixty pound bags or 30 eighty pound bags at 4 inches thick, waste included.
Should a shed slab be bigger than the shed?
No, pour it to the shed footprint. An exposed ledge catches rain and runs it back under the wall plate.
Does a shed slab need to go below the frost line?
Only if it must not move at all. Most shed slabs are poured on grade and accepted as floating, because a shed tolerates slight seasonal movement.
The concrete calculator takes any dimensions you like and hands back the same list.