Yardstickly

Concrete block calculator

Concrete blocks and mortar for a wall, in the block sizes sold where you live.

Pallets of grey concrete paving blocks stacked at a yard
Measure in

Decimals work everywhere. On a keyboard you can also type 10' 6" or 3 1/2.

Wall
ft
ft
sq ft

Optional. Leave blank for a solid wall.

Blocks
in
in
%

How it works

We take the wall's face area, subtract any openings, and divide by the area one block covers including its mortar joint. A US 8 × 8 × 16 in block is nominal: the block is 3/8 in smaller, so with its joint it covers exactly 16 × 8 in, or 1.125 blocks per sq ft. A UK 440 × 215 mm block with a 10 mm joint comes to about 9.9 per m², and an Australian 390 × 190 mm block 12.5 per m².

For mortar, Quikrete's usage chart says one 80 lb bag of Mortar Mix lays about 12 standard blocks, and a 60 lb bag about 9.

Worked examples

A 20 ft wall, 4 ft high, in 8 × 8 × 16 in blocks: 80 sq ft × 1.125 = 90 blocks, or 95 with 5% spare, and 8 bags of 80 lb mortar mix.

A 5 m wall, 1.2 m high: 63 blocks in the UK's 440 × 215 mm size, or 79 in Australia's 390 × 190 mm size, each with 5% spare.

Before you build

Block walls need a concrete footing. Walls that hold back soil, carry a load or stand taller than about 4 ft (1.2 m) usually need reinforcement and may need a permit or an engineer. Check local rules.

Common questions

How many concrete blocks per square foot?

1.125 for standard 8 × 8 × 16 in blocks, because each one covers 16 × 8 in including its mortar joint. In metric, about 9.9 per m² for 440 × 215 mm blocks and 12.5 per m² for 390 × 190 mm blocks.

How many blocks does a bag of mortar lay?

Quikrete's chart says about 12 standard blocks per 80 lb bag of Mortar Mix and about 9 per 60 lb bag. Other brands print their own figure on the bag.

Guides

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