CalculatorEnter your measurements below and it works the answer out.
1.125 standard blocks to the square foot of wall face. A nominal 8 × 8 × 16 block is actually 7 5/8 in tall, so the block plus its 3/8 in mortar joint occupies exactly 8 × 16 in — which is where the 1.125 comes from.
The arithmetic. Work out the area, divide by what one block covers, add 5% waste, round up. Nothing more than that — the value of the page is the coverage figures and the waste allowance, both of which are stated here rather than hidden inside the tool.
Why the waste allowance is 5%. The nominal size is the size the block occupies in the wall, not the size of the block itself. A standard block is manufactured at 7 5/8 by 7 5/8 by 15 5/8 inches, and the missing 3/8 inch on each face is the mortar joint. Laid up, each block therefore takes 8 by 16 inches of wall face, which is 0.889 square feet — so 1.125 blocks per square foot, and 1.5 courses to the foot of height. Every figure on this page comes out of that one substitution.
How it is sold. Block is sold by the pallet, commonly 90 to 108 standard units depending on the producer and the pallet. Five per cent covers breakage and the cuts at corners and openings, which are unavoidable.
Measure the wall face, then think in courses. A block wall is built in courses 8 inches high, so wall height in inches divided by 8 is your course count — and a wall designed to a whole number of courses needs no block cut lengthwise, which is the single biggest saving on a block job. Deduct openings over about 10 sq ft; leave the small ones in, because the blocks cut around an opening are mostly wasted anyway.
Round up to how it is sold. The result below shows three numbers: the raw quantity, the quantity after the 5% allowance, and the whole blocks to buy. You can see exactly where the rounding happened rather than being handed one figure.
Divide your area in square feet by the coverage of one block, then add 5% and round up. At 0.8889 sq ft each, a 200 sq ft job needs 237.
5% is what this calculator adds. The nominal size is the size the block occupies in the wall, not the size of the block itself. A standard block is manufactured at 7 5/8 by 7 5/8 by 15 5/8 inches, and the missing 3/8 inch on each face is the mortar joint. Laid up, each block therefore takes 8 by 16 inches of wall face, which is 0.889 square feet — so 1.125 blocks per square foot, and 1.5 courses to the foot of height. Every figure on this page comes out of that one substitution.
1.125 for a standard 8 × 8 × 16 in block. Each one occupies 8 by 16 inches of wall face, which is 0.889 square feet, and 1 ÷ 0.889 is 1.125. A 100 square foot wall takes 113 blocks before breakage.
Wall length in feet times 0.75, because each block covers 16 inches — three blocks to every four feet. A 24 ft wall is 18 blocks per course.
Twelve. Each course is 8 inches high including the mortar joint, so 96 inches divided by 8 is 12 courses exactly — which is why 8 ft is the standard basement and garage wall height.
Roughly one 80 lb bag of mortar mix for every 12 to 15 standard blocks, or about 3 bags per 100 blocks of pre-blended mix plus sand. It is a range because it depends on how full the joints are struck and whether you are laying face-shell or full bed. Buy to the top of the range; leftover mortar mix keeps if it stays dry.
The nominal size includes the mortar joint; the actual block is 3/8 inch smaller in each direction. A "8 × 8 × 16" block measures 7 5/8 × 7 5/8 × 15 5/8. Designing to nominal dimensions is what lets a wall come out to whole courses with no cutting.
Commonly 90 to 108 standard 8 in units, but it varies by producer and by block size. Ask the yard before you order — a count that is out by one pallet is a second delivery charge.