Brick Calculator

Background.

A wall 20 feet long and 8 feet high, with 20 square feet of doors and windows, laid in standard modular brick with 3/8-inch mortar joints, takes 960 bricks before waste and 1,056 once 10 percent is added for cuts and breakage. Getting to that number needs one step that plain area division misses: every brick occupies its own face plus a share of the mortar around it.

A modular brick's face measures 7-5/8 by 2-1/4 inches, but in the wall it repeats every 8 by 2-5/8 inches, because each brick brings one head joint and one bed joint with it. That repeating module covers 0.1458 square feet, which is 6.8571 bricks for every square foot of wall. Divide the same wall by the bare brick face instead and the count comes to about 1,175, some 22 percent more than you need.

The count matters because bricks are bought in whole units and usually in full packs, and running short in the middle of a wall can mean buying a later production batch whose colour does not quite match the first. Overbuying by several hundred is the opposite mistake. The intermediate figures shown, from gross and net wall area through the module to the count before waste, let you check the estimate line by line against a mason's takeoff rather than accepting a single unexplained total.

Masonry is a standardized system. ASTM C216 covers facing brick, ASTM C270 covers mortar for unit masonry, and Chapter 21 of the International Building Code sets requirements for masonry construction. None of them tells you how many bricks to order, and nothing here replaces structural design. What the arithmetic gives is a face-quantity estimate for one layer of brick, the kind used for a veneer, a garden wall or a fireplace surround. Solid walls two bricks thick, decorative bonds, soldier courses, arches, piers and caps all change the count and are best added separately.

What is brick calculator?

A brick estimate turns a wall's dimensions into a count of bricks by dividing the area to be covered by the area each brick claims in the wall. Wall dimensions are in feet, brick and joint dimensions in inches, areas in square feet, and the purchase count in whole bricks.

Gross wall area is the full rectangular face, length times height. Net wall area is what remains after subtracting doors, windows, vents and anything else that will not be filled with brick. The brick face is the visible length and height of one brick as laid, and the module is that face enlarged by one mortar joint in each direction. Waste covers breakage, cuts at corners and openings, colour blending and layout uncertainty. Mortar, if you supply a usage rate, is estimated in whole bags from the final brick count.

The method suits preliminary face-brick and veneer estimates. It does not design structural masonry, verify code compliance, size footings, specify mortar type, calculate reinforcement or determine wall ties.

How to use this calculator.

1. 01Enter Wall length and Wall height in feet; from metres, multiply by 3.281. For a gable end, run the rectangle below the eaves first, then the triangle above as a separate wall with its full base as the length and half its peak height as the height.
2. 02Enter Opening area in square feet, the total of every door, window and vent: a 3 by 6.67 foot door is 20 square feet. It must be smaller than the wall itself.
3. 03Enter Brick face length and Brick face height in inches, measured on the face you will see, not the bed depth; a US modular brick is 7.625 by 2.25. Enter Mortar joint thickness in inches too, 0.375 for the usual 3/8-inch joint. Metric sizes convert by dividing millimetres by 25.4.
4. 04Set Waste allowance as a percentage for breakage, cuts and colour blending, raising it for walls with many openings, corners or returns.
5. 05Enter Price per brick for a cost estimate, and Mortar bags per 1,000 bricks if you want a bag count. Take that rate from your mortar supplier or mason; the preset 7 is a starting assumption, and 0 leaves mortar out.
6. 06Read Bricks to buy as the minimum whole number, then round up to your supplier's pack size.

The formula.

The formula begins with wall area. A rectangular wall face is length times height. A 20 foot by 8 foot wall has 160 square feet of gross area. If openings total 20 square feet, net brick area is 140 square feet. Opening deductions are applied before waste because bricks are not installed in the empty door or window area; the waste allowance then accounts for practical losses around the remaining brickwork.

The next step is the brick module. Masonry is laid with mortar joints, so the repeating face dimensions are the brick dimensions plus the joint thickness. With a 7.625 inch brick length and a 0.375 inch joint, the horizontal module is 8 inches. With a 2.25 inch brick height and a 0.375 inch joint, the vertical module is 2.625 inches. Dividing each by 12 converts inches to feet. The module area is 0.666667 feet times 0.218750 feet, or 0.145833 square feet.

Bricks before waste are net wall area divided by module area. In the worked example, 140 divided by 0.145833 equals 960. Waste is applied as a multiplier: 10 percent waste means multiplying by 1.10. The result is 1,056 bricks. The count is rounded up only after waste is added, because bricks are bought as whole units: a result of 1,055.2 would still mean buying 1,056.

Joint thickness changes the count more than its size suggests, because it is added to both dimensions of a small unit. On the example wall, 1/2-inch joints cut the count before waste to about 902 bricks, while 1/4-inch joints raise it to 1,024, a spread of more than 12 percent from a quarter-inch change.

Mortar bags are the final brick count divided by 1,000, multiplied by your bags-per-thousand rate, and rounded up to a whole bag. No single rate fits every job, because joint thickness, cored or frogged bricks, waste and workmanship all change how much mortar a wall takes, so the rate is an input rather than a constant.

A worked example.

Frequently asked questions.

References& sources.

1. [1]ASTM International (2024). "ASTM C216-24: Standard Specification for Facing Brick." ASTM.
2. [2]ASTM International (2019). "ASTM C270-19a: Standard Specification for Mortar for Unit Masonry." ASTM.
3. [3]International Code Council (2024). "2024 International Building Code, Chapter 21: Masonry." ICC.
4. [4]National Institute of Standards and Technology (2026). "NIST Handbook 133, Appendix E: General Tables of Units of Measurement." U.S. Department of Commerce.
5. [5]National Institute of Standards and Technology (2008). "Guide for the Use of the International System of Units (SI), NIST Special Publication 811." U.S. Department of Commerce.