Concrete Block Calculator

Find how many concrete blocks a wall needs, plus total material cost.

⏱ Updated: 18 Sep 2026

Calculator

Free concrete block calculator: find how many 8x16 in. CMU blocks a wall needs, plus total material cost.

Blocks Needed
Net Wall Area (sq ft)
Estimated Material Cost
$

Based on standard 8 in. x 8 in. x 16 in. nominal CMU with 3/8 in. mortar joints (112.5 blocks per 100 sq ft). Leave price per block at 0 to see quantity only.

Enter the wall's length and height to calculate how many concrete blocks it takes, and the total cost.

How to Use the Concrete Block Calculator

Enter the wall's length and height, subtract any door or window openings, and the block count updates immediately. Waste and price per block are both editable if you want a tighter or looser cushion, or a running material cost.

Concrete block coverage isn't a guess — it falls straight out of the block's own dimensions. A standard CMU measures 8 in. tall by 16 in. long on its face, and with a 3/8 in. mortar joint on each side, one block plus its joints covers almost exactly 0.89 sq ft of wall:

blocks per 100 sq ft = 100 ÷ (16 in × 8 in ÷ 144) = 112.5

That figure — 1.125 blocks per sq ft — is the constant this calculator runs on. Multiply it by your net wall area (gross area minus openings), add waste for cuts and breakage, and round up, since a mason can't lay half a block.

What Waste Percentage Should I Use?

10% covers typical cutting loss and breakage on a straightforward rectangular wall. Push it toward 15% on a wall with a lot of corners, angled cuts, or a first-time DIY crew — offcuts add up fast once you're trimming block to fit around a doorway or a stepped foundation line.