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How many blocks for a 40 ft wall?

A 40' × 8' wall takes 360 standard 8×8×16 blocks: 12 courses of 30. Buy about 378 to cover breakage and cuts, plus 30 bags of 80 lb mortar mix.

Wall heightAreaBlocksWith 5% extra80 lb mortar bags
2'80 ft²90958
3'120 ft²13514211
4'160 ft²18018915
5'200 ft²22523719
6'240 ft²27028422
8'320 ft²36037830
10'400 ft²45047337

Block wall

Wall
Add up all walls for a building
Doors + windows. 3'×7' door = 21
5% typical, 10% with many cuts
Inches. Use the spacing on your plans
Blocks to buy—
Net wall area—
Courses × blocks per course—
80 lb mortar bags—
80 lb core-fill grout bags—
Grout volume—

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.

Sources: Block wall

  1. Mason Mix No. 1136 product data sheetQuikreteAn 80 lb bag lays up to 13 standard 8" × 8" × 16" blocks.
  2. Core-Fill Grout – Fine No. 1585-08 product data sheetQuikreteAn 80 lb bag yields about 0.68 ft³ and fills the cores of about 3 standard 8" blocks.
  3. Nominal block face 16" × 8" (includes a 3/8" mortar joint)Standard CMU sizing144 ÷ 128 = 1.125 blocks per square foot of wall; courses = height ÷ 8".
  4. Bexel Block Bedding Mortar product data sheetSika MexicanaMetric mode: about 2–2.5 m² per 20 kg bag (≈ 9 kg/m²) with 20 × 40 cm block and a 10 mm joint.
  5. Metric block face 20 × 40 cm (includes a 1 cm joint)Standard LatAm block sizing (12×20×40, 15×20×40)1 ÷ 0.08 = 12.5 blocks per m²; courses = height ÷ 0.20 m.
  6. Scaling mortar and grout by block widthEstimate (no manufacturer figure)Mortar and grout for 4", 6", 10" and 12" block are the 8" figures × width ÷ 8.

Code tables are copied from the documents above and checked against a second copy where noted. Your local code, its edition and amendments govern. Check all math and verify with a licensed engineer and your building department. See the terms & disclaimer.

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. 40' × 8' = 320 ft² × 1.125 = 360 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 40 ft block wall?

About 30 bags of 80 lb mortar mix for a 40' × 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 40 ft wall?

30 blocks per course (40 ft ÷ 16"), and 12 courses for 8 ft of height (8 ft ÷ 8"). A 4 ft high wall is 6 courses of 30.

Other wall lengths

Related calculators

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.