A 10' × 8' wall takes 90 standard 8×8×16 blocks: 12 courses of 8. Buy about 95 to cover breakage and cuts, plus 8 bags of 80 lb mortar mix.
Wall height
Area
Blocks
With 5% extra
80 lb mortar bags
2'
20 ft²
23
24
2
3'
30 ft²
34
36
3
4'
40 ft²
45
48
4
5'
50 ft²
57
60
5
6'
60 ft²
68
71
6
8'
80 ft²
90
95
8
10'
100 ft²
113
119
10
Block wall
Blocks to buy—
Net wall area—
Courses × blocks per course—
80 lb mortar bags20 kg premixed mortar bags—
Total mortar—
80 lb core-fill grout bags—
Grout volume—
Metric: 12.5 blocks per m² (20 × 40 cm face including a 1 cm joint, e.g. 190 × 390 mm block) and about 9 kg of premixed block mortar per m² (Sika data sheet, 10 mm joint). Site-mixed mortar varies with the mix; do a test on your job.
Counts include the waste % and round up. Mortar and grout use Quikrete's yields for 8" block (13 blocks per bag of Mason Mix, 3 blocks' cores per bag of Core-Fill Grout); other widths are scaled by width and are estimates. Rebar size, cell spacing and bond beams come from your plans or local code.
⚠ Check all math and verify with a licensed engineer and your local building department before cutting or building. Results are estimates.
How the count works
Each 8×8×16 block covers 16" × 8" of wall with its 3/8" mortar joint, or 128 square inches, so a wall takes 1.125 blocks per square foot. 10' × 8' = 80 ft² × 1.125 = 90 blocks. The mortar figure uses Quikrete's yield of up to 13 blocks per 80 lb bag of Mason Mix.
Subtract doors and windows before you order: a 3' × 7' door removes about 24 blocks. Corner, half and bond-beam blocks come out of the same total, so give your supplier the count and let them split it by type. Change the height, block width or grout in the calculator above.
FAQ
How many bags of mortar for a 10 ft block wall?
About 8 bags of 80 lb mortar mix for a 10' × 8' wall of 8" block, with 5% extra. That uses Quikrete's figure of up to 13 blocks per bag, so a bag or two spare is wise.
How many courses and blocks per course on a 10 ft wall?
8 blocks per course (10 ft ÷ 16"), and 12 courses for 8 ft of height (8 ft ÷ 8"). A 4 ft high wall is 6 courses of 8.
Disclaimer: Results are estimates for planning and layout only. Check all math yourself and verify with a licensed engineer and your local building department before cutting or building. FramersMath is not a substitute for engineered plans, span tables or code review. See the full disclaimer.