How Many Cinder Blocks for a 10x10 Shed?
Block to buy
95 block
40 ft of continuous stem wall around a 10 by 10 shed, 3 courses of 8 in block, 2 ft tall, 5 % 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.
- Wall length40 ft
- Wall height2 ft
- Openings to deduct0 sq ft
- Block width, nominal8 in
- Grouted cellsEvery 48 in
- Waste allowance5 %
Block to buy95 block
| Net wall area | 80 sq ft |
|---|---|
| Block before waste | 901.125 per sq ft |
| Courses | 330 block per course |
| Mortar to buy | 4.2 cu ft |
| Mortar mix, 80 lb bags | 713 block per bag |
| Cells to grout | 11 |
| Grout | 4.1 cu ft0.15 cu yd |
| Vertical rebar | 44 ft11 bars at 48 in on center, wall height plus a 2 ft lap |
| Joint reinforcement | 80 ftevery other course |
The material list this produces
| Block | 95 |
|---|---|
| Mortar mix, 80 lb bags | 7 |
| Grout, cu yd | 0 |
| Vertical rebar, ft | 44 |
| Joint reinforcement, ft | 80 |
Shed size compared
The six shed sizes people ask about, at the same three courses. The first row is two different sheds, because a 10 by 10 and an 8 by 12 are both 40 ft around and the wall cannot tell them apart. Nothing in this table knows the floor area.
| Shed size | Block to buy | Mortar mix, 80 lb bags | Vertical rebar |
|---|---|---|---|
| 10 by 10 or 8 by 12 ft | 95 block | 7 | 44 ft |
| 10 by 12 ft | 104 block | 8 | 48 ft |
| 12 by 12 ft | 114 block | 9 | 52 ft |
| 10 by 16 ft | 123 block | 9 | 56 ft |
| 12 by 16 ft | 133 block | 10 | 60 ft |
| 10 by 20 ft | 142 block | 11 | 64 ft |
What else matters here
Ninety five block, for a continuous mortared stem wall three courses tall sitting on a footing. If the shed is going on solid blocks under skids instead, which is what a great many sheds this size do, that is a different job and a much smaller number, and this page is not it.
The thing worth carrying away from this size is what the block does not know. An 8 by 12 shed is also 95 block. It has 96 sq ft of floor against this one's 100, it is a visibly different shed, and the material list for the foundation is identical, because a wall is bought by the foot around the outside and both of these are 40 ft around.
That is not a curiosity, it is how to shop. If the floor plan is not settled, changing the shape at a fixed perimeter is free in block, mortar and rebar, and it only costs in the floor deck and the roof. Going from 10 by 10 to 12 by 12 adds eight feet of perimeter and 19 block. Going from 10 by 10 to 8 by 12 adds nothing at all. The table below is every common shed size measured the way the wall measures them.
What this calculator assumes
- Every block here is 8 by 16 nominal on the face, which is the standard unit whatever its width. That works out to 1.125 blocks per square foot of wall, and the figure already contains the 3/8 mortar joint.
- Mortar is the bed and head joints across the face shells, multiplied by 3.6. The multiplier lands the bag count on the coverage printed on the bag, where an 80 pound bag of mortar mix yields about 0.6 cubic feet and lays roughly 13 standard block.
- Grout volume uses the cell section for the block width: about 27 square inches for an 8 inch block, less for a 4 or 6 and more for a 10 or 12. Fully grouting an 8 inch wall works out near 0.28 cubic feet per square foot of wall, which is the figure the block industry publishes.
- Vertical bars are one per grouted cell. On a fully grouted wall they are figured at 48 inches on center instead, because grouting every cell does not mean putting a bar in every cell.
- Horizontal joint reinforcement is every other course, which is 16 inches.
Questions people ask
How many cinder blocks for a 10x10 shed?
95 block for a continuous stem wall three courses tall around the 40 ft perimeter, including a five percent waste allowance.
Does an 8x12 shed need the same blocks as a 10x10?
Yes, exactly the same 95. Both are 40 ft around, and the wall follows the perimeter rather than the floor area.
Is a block stem wall the same as putting a shed on blocks?
No. A stem wall is a continuous mortared wall on a footing. Setting a shed on solid blocks under its skids is a different foundation with a far smaller block count.
The concrete block calculator takes any dimensions you like and hands back the same list.