Brick Calculator: How Many Bricks and Mortar Bags
Enter the wall size, take off windows and doors, pick US modular or UK metric bricks and set the joint. You get bricks per square foot or metre, the order quantity with waste, and mortar bags. After switching units, re-enter your measurements.
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Formula
- Bricks per area:
1 / ((brick length + joint) x (brick height + joint)) - Net area:
wall length x wall height - openings - Bricks to order:
net area x bricks per area x (1 + waste / 100), rounded up - Mortar per brick:
(length + joint) x (height + joint) x depth - length x height x depth - Mortar volume is the theoretical joint volume x 1.4 (practical loss, see assumptions)
- Bags:
mortar volume / bag yield, rounded up
Assumptions
- US modular bricks are 7-5/8 x 2-1/4 x 3-5/8 in; UK metric bricks are 215 x 65 x 102.5 mm (actual sizes).
- A single-skin wall laid in stretcher bond, joint the same on bed and perpend.
- The waste percentage applies to both bricks and mortar.
- Mortar includes a built-in 40% allowance above the theoretical joint volume, because practical premix use runs about 40% over (droppings, bed and perpend fill, tooling).
- Bag yield is an input because brands differ; 17 L is about 0.6 cubic feet.
Worked example
A 20 ft by 8 ft wall in US modular brick with 10 mm joints. Area is 160 ft2 = 14.864 m2. Bricks per m2 = 1 / (0.203675 x 0.06715) = 73.12, or 6.79 per ft2. Plain count is 1,086.8; with 10 percent waste it is 1,195.5, so 1,196 bricks. Theoretical mortar with waste is 287.1 litres; with the 40% practical allowance it is 402.0 litres, which is 24 bags of 17 L (23.6 rounded up).
Frequently asked questions
How many bricks are in a square foot?
With US modular bricks and a 3/8 inch joint a wall takes about 6.86 bricks per square foot. With a 10 mm joint the figure is 6.79. With UK metric bricks and a 10 mm joint a square metre takes 59.26 bricks.
How do I work out the bricks for a wall?
Multiply length by height, subtract openings, then multiply by bricks per unit area. A 20 by 8 ft wall is 160 square feet, and 160 x 6.79 = 1,087 bricks. Adding 10 percent for waste gives 1,196.
How much mortar do I need for bricklaying?
The calculator finds the volume of the joints around each brick. For that 20 by 8 ft wall the theoretical joint volume is about 287 litres with 10 percent waste. Practical premix use runs about 40 percent above that, so the calculator adds a built-in 40 percent allowance: about 402 litres, which is 24 bags if one bag yields 17 litres (about 0.6 cubic feet). Check the yield printed on your bag.
How much waste should I allow?
Ten percent is a common allowance for straight walls. Allow 15 percent or more for many corners, curves, cut bricks or soft handmade bricks. The result is always rounded up to whole bricks and whole bags.