Concrete Block Calculator

Calculate the number of concrete blocks needed.

Mason ReidFounder and Lead Estimator at MeasureThen

Last updated 2026-08-21

What Is a Concrete Block Calculator?

A concrete block calculator tells you how many standard concrete masonry units, or CMUs, you need for a wall or foundation. You enter the wall length and height and the block size, and it returns a block count you can order. Contractors and DIYers use it to price materials before breaking ground.

How It Works

Blocks = ceil(Wall area ÷ (16 × 8 ÷ 144)) = ceil(Area × 1.125).

Example

A 20 ft × 8 ft wall needs 180 standard 8x8x16 blocks.

How to Calculate

Measure the wall length and height in feet. A 20 ft by 8 ft wall covers 160 square feet.
Select the block size. The standard 8x8x16 block has a 16 by 8 inch face that covers 0.89 square feet.
Multiply the wall area by 1.125, which is the inverse of the block coverage per square foot.
For 160 square feet, the tool returns about 180 standard blocks.
Add 5% for cuts and breakage, bringing the order to roughly 189 blocks.

Concrete Block Sizes and Coverage

Block Size (nominal)	Face Coverage (sq ft)	Blocks per Sq Ft
4x8x16	0.89	1.125
8x8x16	0.89	1.125
12x8x16	0.89	1.125
16x8x16	0.89	1.125
8x8x8 (half)	0.44	2.25

Sources

Frequently Asked Questions

What size is a standard block?

The nominal 8x8x16 block has a 16 × 8 in face and covers 0.89 sq ft per block.

Do all block widths use the same face?

Yes — 4, 8, and 12 in blocks share the same 16 × 8 face, so block count is identical.

Should I add for waste?

Add 5% for cuts and damage; more for walls with many openings.

Mason ReidFounder and Lead Estimator at MeasureThen

Mason Reid founded MeasureThen after two decades of hands-on work in construction and estimating. Across residential and light commercial projects, he sized concrete pours, framed walls, hung drywall, and priced out roofing, fencing, and deck work — learning the exact math that every job depends on. At MeasureThen he writes the formulas, checks every calculator against real-world assumptions, and makes sure each one is simple enough for a homeowner to trust and a contractor to use. When he is not measuring twice, he is helping projects stay on budget.

Every MeasureThen calculator uses simple, transparent formulas and standard industry assumptions drawn from common construction practice. We show the math behind each result and include worked examples so you can follow along and double-check the numbers. Results are estimates: materials, labor, and pricing vary by region and market, so always confirm important figures with a licensed professional and your local building codes.