Concrete Block Calculator

Concrete Block Calculator for Cinder Block Walls

The Concrete Block Calculator estimates how many CMU blocks, mortar bags, and dollars you need for a rectangular block wall. Enter wall dimensions, block face size, and price to get a material list.

How block count is calculated

Wall area in square feet is multiplied by 144 to convert to square inches, then divided by the block face area:

$$\text{Blocks} = \frac{\text{Wall height (ft)} \times \text{Wall width (ft)} \times 144}{\text{Block height (in)} \times \text{Block width (in)}}$$

Standard US blocks include 16" × 8", 12" × 8", and 8" × 8" face sizes. Add 10% waste for cuts and breakage.

Mortar estimate

About three 40 lb mortar bags cover 100 blocks. Divide your block count by 33.3 and round up to estimate bags.

Frequently Asked Questions

How many concrete blocks do I need for a 10 by 50 foot wall?

A 10 ft by 50 ft wall is 500 ft². With standard 16" × 8" blocks (128 in² face), you need about 563 blocks before waste. Add 10% extra for a safer order.

How much mortar do I need for 100 blocks?

Plan on about three 40 lb bags of mortar per 100 blocks. Some manufacturers recommend 2.6 bags per 100 blocks for thin joints.

Should I order extra blocks?

Yes. Order at least 10% more than the calculated count to cover broken blocks, cuts around openings, and layout changes.

What is the standard concrete block size?

The most common US block is 16 inches long by 8 inches tall with an 8 inch width (depth). Face dimensions used for wall layout are 16" × 8".

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