Concrete Block Calculator

Use it when your task matches one of these common needs: Estimate block count for a simple wall. See approximate course count and blocks per course. It works best when you already know wall length, wall height, block length, block height, opening area, and waste percent.

In plain language: The calculator uses wall area = length x height, net area = wall area - openings, adjusted area = net area x (1 + waste percent / 100), nominal block face area = block length x block height / 144, and blocks needed = adjusted area / block face area rounded up. The examples on the page are there so you can compare your inputs with a concrete block wall example before copying the answer.

Wall length and height: the finished wall face dimensions in feet. Nominal block size: the common wall-layout module, such as 16 by 8 inches, which usually includes the mortar-joint spacing. Openings: door, window, or other areas subtracted before waste is added. Waste percent: extra blocks for cuts, broken units, corners, and layout changes.

Read the headline estimate first, then check the material, waste, coverage, and unit lines. For project tools, the supporting lines are often the difference between a rough idea and a list you can actually shop from.

This is a block count estimate, not structural design. Block walls need professional review for footings, drainage, reinforcement, grout, lintels, mortar, bond pattern, corners, retaining-wall loads, permits, and local code. Also check whether the block size is nominal, whether openings were subtracted before waste, and whether corners, half blocks, reinforcement, mortar, grout, and footings were planned separately.

A common nominal 8 by 16 inch block face covers about 8/9 square foot, so it takes about 1.125 blocks per square foot before waste. That is about 113 blocks for 100 square feet, or about 119 blocks with 5% waste.

Use the nominal size for a wall-layout estimate unless your supplier tells you otherwise. The actual block is usually smaller because the nominal size includes the mortar joint space.

A door or window removes wall area, so subtract openings first. Then add waste to the remaining wall area for cuts, broken blocks, corners, and layout changes.

No. It estimates block count, courses, and blocks per course only. Mortar, grout, reinforcement, footings, lintels, drainage, and labor need their own estimate and code check.

Use it only for a rough block count. Retaining walls need drainage, reinforcement, soil-load checks, permits, and local code review, so the calculator cannot approve the design.

No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.