GlenCalc

Brick and block calculator

Enter the size of the wall and the brick or block. You get the number of units to buy, allowing for the mortar joint and breakage, and a rough count of mortar bags.

Doors, windows and vents.

3/8 in is standard.

Pick the conditions closest to your job. Each adds the allowance shown for offcuts, breakage and uneven ground. Choose Custom to enter your own.

Printed on the bag. 80 lb bags of mortar mix typically lay roughly 30 to 40 bricks.

Your answer

Bricks576 bricksIncluding 5% extra
Mortar mix17 bagsRough: 35 bricks per bag
Wall area80 sq ft
Bricks per sq ft6.857
Before extra548.6 bricks
  • This counts a single layer (one wythe). A double brick wall needs twice as many.

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How we worked it out

Updated as you change the numbers.

  1. Wall area = 20 ft × 4 ft = 80 sq ft.
  2. Each unit with its joint covers (7.625 + 0.375) × (2.25 + 0.375) = 21 sq in, so 144 ÷ that = 6.857 per sq ft.
  3. Units = 80 × 6.857 × 1.05 = 576, rounded up to 576.
  4. Mortar bags = 576 ÷ 35, rounded up = 17.

Method and assumptions

Bricks and blocks are made slightly smaller than their nominal size so that, with a 3/8 in mortar joint, they lay out on a neat grid. A modular brick with its joint takes up 8 × 2 5/8 in, so a square foot holds about 6.86. A standard block with its joint takes up 16 × 8 in, so a square foot holds 1.125.

Mortar yield depends on the joint, the units and the mason, so the bag count is a rough guide. Use the yield printed on your mortar bag.

Tips

  • Bricks vary a little in size between makers. Check the actual dimensions on the product sheet and use “Other size” if they differ.
  • Walls taller than a few feet, retaining walls and anything structural need footings and reinforcement designed to your local code.

Questions

How many bricks are in a square foot?

About 6.86 modular bricks per square foot of wall with a 3/8 in mortar joint, or about 7.2 with 5% extra. A 100 sq ft wall takes about 686 bricks before extra.

How many concrete blocks do I need per square foot?

1.125 standard 8 × 8 × 16 blocks per square foot. A wall 20 ft long and 4 ft high (80 sq ft) needs 90 blocks, or 95 with 5% extra.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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