Concrete Block Calculator

Plan concrete blocks / CMU (concrete masonry units), optional mortar and entered material costs.

Quantity estimate only. This does not design a structural masonry wall.

Your wall

Decimal feet are welcome; maximum 10,000 ft.

Maximum 1,000 ft. Use up to six decimal places.

Concrete block size

Thickness × face height × face length, in inches.

A common “8 × 8 × 16” block is a nominal masonry size. Actual units are typically smaller so mortar joints complete the nominal module. This calculator uses nominal face dimensions for layout estimates. Thickness does not change the face block count.

Openings (optional)

Add doors, windows or other openings. Enter dimensions in feet and the number of identical openings. Positions in the diagram are illustrative.

Up to 20 rows and 200 openings total.

Block allowance

Applied once, after the opening-adjusted physical block estimate is rounded up.

Mortar and costs (optional)

Use the coverage/yield information for the mortar product you plan to buy. Leave blank to omit mortar quantities.

Leave blank to omit block cost.

How it works

We round wall height up to whole courses and wall length up to whole blocks per course. Multiply these counts to estimate the whole wall. For openings, subtract their area-equivalent blocks, round the physical block estimate up, then apply your purchasing allowance and round up again.

Mortar bags use your entered blocks-per-bag coverage and the final blocks to buy. Costs include only components you priced.

Concrete block vs. CMU

CMU means concrete masonry unit. Concrete block is the more familiar homeowner term.

Nominal vs. actual block size

Nominal dimensions describe the block-and-mortar module. Manufactured units are typically smaller to accommodate mortar joints. Use nominal face dimensions here, not actual unit dimensions.

Openings

Opening deductions are area-equivalent estimates. Actual bond patterns, cuts and lintels can change material needs. The allowance helps with purchasing; it does not design the opening. Overlap and opening positions are not modeled.

Quantity estimate, not structural design

RockUtility estimates materials from dimensions you supply. It does not determine wall thickness, reinforcement, grout, bond beams, lintels, footings or structural adequacy. Material totals exclude unpriced items, reinforcement, grout, footing, delivery, tax and labor. Confirm quantities, mortar yield and construction requirements before buying.