Concrete block wall module planner.

Worked example

A 24 ft x 8 ft wall is 288 in. x 96 in. On the 8 in. module that is 36 modules long and 12 courses high, so 18 full 16 in. units per course and 216 full units in all, with no cutting. A 36 in. door that is 80 in. tall needs a masonry opening 36 + 4 = 40 in. wide, which is on the module, and 80 + 2 = 82 in. high, which is not, so the next height on the module is 88 in.

Method and sources

Module rules come from the Concrete Masonry & Hardscapes Association TEK 05-12, Modular Layout of Concrete Masonry (retrieved 2026-10): standard modules are typically 8 in. vertically and horizontally (4 in. for some uses); actual unit dimensions are typically 3/8 in. less than nominal so the module holds with 3/8 in. joints; plan dimensions should be evenly divisible by 8 in. so courses use full or half units; opening widths should generally be 4 in. larger than the door or window width; window openings are typically 8 in. greater than the window height when a 4 in. sill is used; door openings are commonly 2 or 4 in. greater than the door height. The standard unit is nominally 8 in. high and 16 in. long, and half-high units are 4 in. high (CMHA TEK 02-02B, Considerations for Using Specialty Concrete Masonry Units, retrieved 2026-10). Arithmetic: modules per course = length / 8; a nominal unit is two modules (16 in.), so an odd count adds one half unit per course; courses = height / block height. Limits: this is a nominal planning dimension, not the as-built size, and it counts units before deducting openings. Use the concrete block and mortar calculator for mortar and bags, and follow the drawings and your mason for corners, bond beams and special units.

FAQ

How many courses of block is an 8 foot wall?

With standard 8 in. high block, 96 in. / 8 = 12 courses. With half-high 4 in. block it is 24 courses.

Why do block walls come in multiples of 8 inches?

CMHA TEK 05-12 says standard modules are typically 8 in. in both directions and that plan dimensions should be evenly divisible by 8 in. so full or half units fit without cutting.

How big should a door or window opening be in block?

Per TEK 05-12, generally 4 in. wider than the door or window, window openings typically 8 in. taller than the window, and door openings commonly 2 or 4 in. taller than the door.

Is a block 8 x 16 inches?

That is the nominal size (TEK 02-02B: 8 in. high, 16 in. long). TEK 05-12 says actual dimensions are typically 3/8 in. less, so that 3/8 in. joints keep the module.