Concrete & Masonry calculator

Concrete Block CalculatorCMU Blocks for a Wall

Calculate concrete block quantity for a wall from length, height, block face dimensions, openings and waste allowance. Estimate full CMU units before ordering.

Updated August 20, 2026

✓Instant estimateNo sign-up required

✓Clear formulaSee how the result is built

✓Editable inputsMatch your product

✓Practical roundingPlan real purchase units

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Project details

Enter your measurements and material details.

Planning estimate only. Verify product specifications and project requirements before ordering.

💡Tip:

Nominal block dimensions include mortar joints; use the layout dimensions appropriate to the system.

How the Concrete Block Calculator works

The calculator finds net wall area after openings, converts the block face dimensions to square feet and divides the wall area by the face area. A waste percentage is then applied and the count is rounded up.

Formula

Blocks = net wall area ÷ block face area × waste factor, rounded up.

Measure before you buy

Measure the actual wall length and height and subtract large openings. Use the nominal module or manufacturer layout dimensions that match the masonry system rather than physical block dimensions if the joints are part of the module.

Corners, bond beams and special units are not separated from standard blocks.
Cut blocks and breakage justify a small allowance.
Structural reinforcement and grout are separate material calculations.

Common questions

How many 8x8x16 blocks are in 100 square feet?

A nominal 8x8x16 block covers about 0.89 square feet of wall face, so roughly 113 blocks before waste.

Should mortar joints be included?

Use nominal modular dimensions when the system assumes standard joints.

Can I subtract windows and doors?

Yes. Enter their combined area as openings.

Does this count corner blocks?

No. It estimates total face units, not special unit types.

Does it calculate mortar?

No. Use the mortar calculator separately.

Worked example: Concrete Block Calculator

Using the example inputs shown in the calculator — Wall length (ft) = 30, Wall height (ft) = 8, Openings (sq ft) = 40, Block face width (in) = 16, Block face height (in) = 8 — the result is 237 blocks. This demonstrates the formula with a complete set of numbers rather than a hidden assumption.

The result breakdown also shows Net wall area: 200 sq ft; Block face area: 0.889 sq ft. Replace the example values with field measurements and the exact product coverage, yield or package size you plan to buy.

For this concrete block calculator, the inputs with the greatest practical effect are wall length, wall height and openings. Recalculate when any of those change; do not reuse a result from a different room, run, layer depth or product specification.