How many cinder blocks for a 10×10 shed?
A block foundation wall three courses high (2 feet) around a 10 × 10 ft shed runs 37 feet 4 inches on its centre line. That is 28 blocks per course, 84 in all, or 89 blocks with 5% extra, laid with about 8 bags of 80 lb mortar mix, including 15% extra.
How to work it out
- 3 courses of 8 in (block + ⅜ in joint) · 37.3 ft ÷ 16 in = 28 blocks per course
- 74.7 sq ft ÷ 0.889 sq ft per block face + 5% = 89 blocks
- Mortar: 84 blocks ÷ 13 per 80 lb bag + 15% (BIA suggests 15–25%) = 8 bags
A low block wall under a shed — a perimeter “stem wall” sitting on a footing — is the usual reason people ask this. Three courses is used as the example; change the height to match your plans.
Adjust for your project
More options: Openings · Extra
- Courses (rows)
- 3 courses
- Blocks per course (to the next half)
- 28
- Blocks per square foot
- 1.125 per sq ft
- Wall area (net of openings)
- 74.7 sq ft
- Mortar mix, 80 lb bags (incl. 15% extra)
- 8 bags
- Actual block size
- 7-5/8 × 7-5/8 × 15-5/8 in
- Count corner, end and bond-beam units separately if your wall needs them; ask the supplier which shapes they stock.
Blocks around a 10×10 shed by wall height (5% extra)
| Wall height | Blocks to buy | Mortar mix, 80 lb bags (incl. 15% extra) |
|---|---|---|
| 2 courses | 59 blocks | 5 bags |
| 3 courses | 89 blocks | 8 bags |
| 4 courses | 118 blocks | 10 bags |
| 6 courses | 177 blocks | 15 bags |
Measure on the centre line
Around the outside, a 10 × 10 ft outline is 40 ft. But at every corner one block covers the end of both walls, so counting the outside length overstates the blocks. Measure along the middle of the wall instead: 10 ft minus one block thickness (8 in) per side, × 4 = 37 ft 4 in. At 16 in per block that is exactly 28 blocks a course.
Three courses build 24 in of wall. If your plans call for the wall to start below grade on a footing and rise above it, count every course, including the buried ones. The footing under the wall is a separate pour — the footing calculator does the concrete for a 12 in square section.
Doors, piers and other options
Leave an opening in the wall where the shed door will be only if your plans show one — many sheds sit on a continuous wall with the floor framed over it. For a lighter base, some people use solid concrete piers or deck blocks instead; for a slab floor, see how much concrete for a 10×12 shed. Whether a block foundation needs reinforcement or grouted cores is set by your local rules.
Different size? Use the full Concrete Block Calculator.
What you’ll need
- Mason’s line and line blocksBudget price
Bright braided line stretched between line blocks keeps each course of block or brick straight and level, and marks out slab edges.
See options on Amazon (opens in a new tab) - Brick trowelBudget price
Spreads and furrows the mortar bed and butters the ends of each block or brick. A 10–11 in trowel suits most hands.
See options on Amazon (opens in a new tab) - 4 ft levelMid-range price
Checks forms for level and slope, and plumbs block, brick and posts. A 4 ft level bridges small bumps that fool a short one.
See options on Amazon (opens in a new tab)
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Frequently asked questions
How many cinder blocks for a 10×10 shed with a 4-course wall?
118 blocks with 5% extra (4 courses).
How many cinder blocks for a 10×12 shed, 3 courses?
98 blocks with 5% extra, on a centre line of 41 feet 4 inches.
Other common sizes
- 8×8×16 block actual size — 7-5/8 × 7-5/8 × 15-5/8 in (194 × 194 × 397 mm)
- How many blocks per square foot — 1.125 blocks per sq ft (119 per 100 sq ft with 5% extra)
Sources
- CMHA (formerly NCMA) CMU-TEC-001-23 — Concrete masonry unit shapes, sizes, properties and specifications (opens in a new tab) — Specified dimensions are 3/8 in less than nominal, so an 8×8×16 block is 7-5/8 × 7-5/8 × 15-5/8 in; nominal thicknesses 4–16 in; ±1/8 in tolerance.
- CMHA (formerly NCMA) TEK 04-02A — Estimating concrete masonry materials (opens in a new tab) — Each 8×16 unit covers 8/9 sq ft, so 112.5 units per 100 sq ft (119 with 5% waste); grout per 100 sq ft by unit width and core spacing (Table 3); cores filled per 80 lb grout bag (Table 4); one 80 lb bag of preblended mortar lays about 16 CMU with face-shell bedding (Table 2).
- Quikrete Mortar Mix (No. 1102) data sheet (opens in a new tab) — Each 80 lb bag lays up to 37 standard bricks or 13 standard 8×8×16 blocks.