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Concrete Block Calculator

A concrete block calculator works out how many blocks a wall needs and the mortar to lay them, from the wall length and height. It uses standard 8×8×16 in CMU, the most common block — and a cinder block is calculated exactly the same way.

Your measurements

Result

Block is heavy, locally-bought material, so the win is getting the count and mortar right before you order a pallet — no second delivery, no leftover blocks.

How it is calculated

A standard 8×8×16 in block covers about 0.89 sq ft of wall face, so you need about 1.125 blocks per square foot. We add a small waste allowance and estimate mortar at roughly three 80 lb bags per 100 blocks (3/8 in joints).

Steps

Enter the wall length and height (or its area).
Leave the small waste allowance for breakage and cuts.
Read the block count for standard 8×8×16 in units.
Grab the mortar bags shown to lay them.
For a structural wall, add rebar and core-fill separately.

Worked example

A 25 ft wall, 8 ft high (200 sq ft) needs about 236 standard blocks and roughly 8 bags of mortar.

Common questions

How many concrete blocks per square foot?

About 1.125 standard 8×8×16 in blocks per square foot of wall. The calculator multiplies your wall area by that and adds waste.

Is a cinder block the same as a concrete block?

For estimating, yes — same nominal 8×8×16 in size and count per square foot. This calculator covers both.

How much mortar for a block wall?

Roughly three 80 lb bags per 100 blocks with standard joints. The result shows the bag count.

Do I need rebar in a block wall?

Structural and retaining walls do — vertical bars in grouted cores to an engineer's spec. This sizes blocks and mortar, not the steel.