How Many Cinder Blocks for a 10x16 Shed?
Block to buy
123 block
52 ft of continuous stem wall around a 10 by 16 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 length52 ft
- Wall height2 ft
- Openings to deduct0 sq ft
- Block width, nominal8 in
- Grouted cellsEvery 48 in
- Waste allowance5 %
Block to buy123 block
| Net wall area | 104 sq ft |
|---|---|
| Block before waste | 1171.125 per sq ft |
| Courses | 339 block per course |
| Mortar to buy | 5.4 cu ft |
| Mortar mix, 80 lb bags | 913 block per bag |
| Cells to grout | 14 |
| Grout | 5.3 cu ft0.19 cu yd |
| Vertical rebar | 56 ft14 bars at 48 in on center, wall height plus a 2 ft lap |
| Joint reinforcement | 104 ftevery other course |
The material list this produces
| Block | 123 |
|---|---|
| Mortar mix, 80 lb bags | 9 |
| Grout, cu yd | 0 |
| Vertical rebar, ft | 56 |
| Joint reinforcement, ft | 104 |
Stem wall height compared
The same 52 ft of wall from two courses to six. On a sloping site the two ends of the shed are on different rows of this table, so the honest order is the taller one.
| Stem wall height | Block to buy | Courses | Mortar mix, 80 lb bags |
|---|---|---|---|
| 16 in | 82 block | 2 | 6 |
| 24 in | 123 block | 3 | 9 |
| 32 in | 164 block | 4 | 12 |
| 40 in | 205 block | 5 | 15 |
| 48 in | 246 block | 6 | 18 |
What else matters here
One hundred and twenty three block for a mortared stem wall, and as on every page in this set, that is the continuous wall rather than blocks set under skids.
A 10 by 16 is long enough that the ground under it is rarely level, and that is the number nobody computes. A slope of six inches across sixteen feet is barely visible standing on it and is most of an extra course of block at one end. The wall has to arrive level at the top whatever the ground does underneath, so the downhill end simply gets more block, and the order has to cover the tall end rather than the average.
The practical way to find out is a string line and a line level, or a long straight board with a spirit level on it, pulled from the high corner to the low one before anything is dug. Measure the drop, add it to the height you wanted at the high end, and read that row of the table below. Ordering off the average leaves you short by the exact amount the ground fell, which is the one shortfall that stops the job dead, because a stem wall cannot be finished at one end and left at the other.
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 10x16 shed?
123 block for a continuous stem wall three courses tall around the 52 ft perimeter, including a five percent waste allowance.
What if the ground under the shed is not level?
The wall still has to arrive level at the top, so the downhill end takes more courses. Measure the drop from the high corner to the low one and order for the tall end, not the average.
How do I measure the fall across a shed site?
A string line with a line level on it, or a long straight board with a spirit level, pulled from the high corner to the low one before anything is dug.
The concrete block calculator takes any dimensions you like and hands back the same list.