Block Size Calculator
Enter the wall's length and height, any openings such as doors and windows, and the block size. The calculator counts the blocks with 5% for cuts, the mortar and the number of courses.
- Blocks needed
- Mortar
- Courses
Enter openings as a total area in the same units squared.
An 8 × 16 in block covers about 0.89 sq ft of wall. A wall 20 ft long and 6 ft high is 120 sq ft. It takes 135 blocks, or 142 with 5% for cuts, about 5 bags of mortar and 9 courses.
Concrete block chart
With 5% waste. Search for a wall.
| Wall area | US 8 × 16 in blocks | UK 440 × 215 blocks |
|---|---|---|
| 50 sq ft (4.6 m²) | 60 | 49 |
| 100 sq ft (9.3 m²) | 119 | 97 |
| 150 sq ft (13.9 m²) | 178 | 145 |
| 200 sq ft (18.6 m²) | 237 | 193 |
| 300 sq ft (27.9 m²) | 355 | 290 |
| 400 sq ft (37.2 m²) | 473 | 386 |
| 500 sq ft (46.5 m²) | 591 | 482 |
| 1000 sq ft (92.9 m²) | 1182 | 964 |
Blocks.
Wall area and blocks
US 8 × 16 in blocks. Slide the wall area.
The wall is drawn with its courses.
How to count blocks
Wall to blocks. Step through it.
Measure
Length and height.
Set out the first course dry to check the bond.
Hollow, solid or aerated
Block types. Compare them.
US standard.
UK standard.
Light.
Aerated blocks are light and insulate well, dense blocks carry heavy loads.
Before you build
Block wall checks. Tick each item.
Tick each item as you go.
Use a string line on every course to keep it level.
What you get
Block counting. Each tile explains one result.
Count.
Wall.
Bags.
Rows.
5%.
Mortar joints are about 3/8 in or 10 mm.
Frequently Asked Questions
No question matches that search.
How many blocks do I need?
Divide the wall area by the face of one block with its joint and add five per cent.
How many blocks in a square foot?
About one point one three standard eight by sixteen inch blocks.
How many blocks per square metre?
About ten UK blocks of four hundred and forty by two hundred and fifteen millimetres.
How much mortar for a block wall?
About one eighty pound bag for every thirty US blocks.
How many blocks for a hundred square foot wall?
About one hundred and nineteen with waste.
Do block walls need rebar?
Retaining and load bearing walls usually do.
How big is a cinder block?
A standard one is about seven and five eighths by fifteen and five eighths inches.
Order the right number of blocks
Count your blocks and mortar before you start so the wall goes up without a second trip.
More size calculators
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