What this calculator does
Find out how many bricks to buy for a wall, and how much mortar to mix with them. Each brick in a wall takes up its own face plus half of the mortar joint around it. A joint is the strip of mortar between two bricks. Half a joint on every side works out to one full joint added to the brick's length and to its height.
Divide the wall's area by that patch, and you have the number of bricks. This calculator does that for any brick size and joint thickness, in US or metric units. Then it adds extra for broken and cut bricks.
It also works out the mortar. That's the space between the bricks, through the thickness of a wall one brick deep (sometimes called a half-brick wall). It turns that into premixed mortar bags, using a typical amount per bag that you can change.
The result is an estimate of what to buy. Wall ties, footings, movement joints and structural needs come from your local building code. Mix and use the mortar as its maker instructs.
Where it's used
Why this math matters outside the classroom:
- Garden walls. A 20 × 3 ft garden wall has 60 ft² of face, which at about 6.9 modular bricks per square foot is roughly 412 bricks before waste.
- Mortar joints. Masons add the 3/8 in joint to each side, so a 7⅝ × 2¼ in brick covers an 8 × 2⅝ in patch of wall.
- Ordering pallets. Builders add a waste allowance for broken and cut bricks before rounding the order up to whole pallets.
- Planter projects. Homeowners count the bricks for a small raised planter by finding the face area of each side and adding them.
- Comparing brick sizes. Students compare how many bricks a 100 ft² wall needs with two brick sizes by dividing the same area by each face.
Grade level and standards: Grades 6–7; Common Core State Standards for Mathematics 7.G.B.6. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Choose US units (feet and inches) or metric units (meters and millimeters).
- Enter the wall as length × height. Or enter the area directly, with doors and windows already taken out.
- Enter the actual brick size and how thick the mortar joint is. The defaults are a US modular brick with ⅜ in joints, and a common metric brick with 10 mm joints.
- Set the extra for waste and how much mortar a bag makes. Then read the bricks to buy, the mortar and the bags.
What the inputs mean
- Wall area
- The face area to be bricked, with doors and windows already taken out.
- Brick length
- Use the actual (measured) size, not the "nominal" size (the brick plus one joint, used for planning), because the calculator adds the joint separately. A US modular brick is about 7⅝ × 2¼ × 3⅝ in. A common metric brick is 215 × 65 × 102.5 mm.
- Brick depth (wall thickness)
- The brick's depth is how thick a wall one brick deep will be. It only changes the mortar amount, not the brick count.
- Mortar joint
- The finished mortar joint between bricks. Enter 0 for bricks laid dry, with no mortar.
- Waste allowance
- This extra is added to both the bricks and the mortar. 5% suits plain walls. Patterns, corners and many openings need more.
- Mortar yield per 80 lb bag
- How much mortar one bag makes. About 0.67 ft³ per 80 lb bag of premix is typical. The bag lists the exact amount.
- Mortar yield per bag
- Typical value: roughly 13 L for a 25 kg bag of premixed mortar. Check the bag.
Formula and method
face per brick = (brick length + joint) × (brick height + joint) bricks in the wall = wall area ÷ face per brick bricks to buy = bricks in the wall × (1 + waste % ÷ 100), rounded up mortar per brick = brick depth × (face per brick − brick length × brick height) mortar = bricks in the wall × mortar per brick × (1 + waste % ÷ 100) bags = mortar ÷ yield per bag, rounded up
"Face per brick" is the patch of wall one brick covers, joints included. Adding one joint to each side's measurement counts each brick's share of the joints exactly once: half a joint on each side. You enter brick sizes in inches or millimeters. So the calculator divides the face by 144 (square inches in a square foot) or 1,000,000 (square millimeters in a square meter) to match the wall area.
Picture a box made of the brick plus its joints, as deep as the wall. The mortar for one brick is that box minus the brick itself. "Yield per bag" is how much mortar one bag makes. In US units, the calculator divides cubic inches by 1,728 to get cubic feet. In metric, it divides cubic millimeters by 10⁹ (a billion) to get cubic meters.
Worked example
A wall 20 ft long and 6 ft high is built with 7⅝ × 2¼ × 3⅝ in bricks, ⅜ in joints, a 5% waste allowance and 80 lb mortar bags that yield 0.67 ft³.
- Wall area: 20 × 6 = 120 ft².
- Face per brick: (7.625 + 0.375) × (2.25 + 0.375) = 8 × 2.625 = 21 in², or 0.1458 ft².
- Bricks in the wall: 120 ÷ 0.1458 = 822.9 (6.857 per ft²).
- With 5% waste: 822.9 × 1.05 = 864 bricks.
- Mortar per brick: 3.625 × (21 − 17.156) = 13.93 in³; total 822.9 × 13.93 ÷ 1,728 × 1.05 = 6.97 ft³.
- Bags: 6.97 ÷ 0.67 = 10.4, rounded up to 11 bags.
Result: Buy 864 bricks, and about 6.97 ft³ (0.26 yd³) of mortar, which is 11 bags of 80 lb premix.
Understanding the result
Bricks are usually sold in packs or on pallets, so round the count up to your supplier's unit. Buying all the bricks for a job at once also keeps the color the same, since it can vary between batches.
The mortar number covers the joints of the wall itself. Mortar dropped while you work is extra. So is mortar used to fill cavities or to bed a damp-proof course (a moisture barrier near the base). Many masons allow more extra for mortar than for bricks.
Assumptions and limitations
- The wall is one brick thick (a half-brick or single-wythe wall). It's laid in a running pattern of whole bricks, with each row offset from the one below.
- All the joints, both under and between bricks, are full and the same thickness.
- The same waste percentage applies to bricks and mortar.
- This estimates materials; it isn't a structural design. It doesn't check wall height, ties, lintels (beams over openings), footings or movement joints. Follow local codes and the mortar maker's instructions.
- It doesn't handle double-thickness walls, headers, decorative patterns, frogs (indents in the brick) or bricks with holes. All of these change the mortar amount.
- How much mortar a bag makes varies by product. The defaults are typical numbers, so replace them with the amount on your bag.
Frequently asked questions
How many bricks are in a square foot?
With a US modular brick (7⅝ × 2¼ in) and ⅜ in joints, each brick takes 21 in². So a square foot holds 144 ÷ 21 = 6.86 bricks. When modular brick is laid so that three rows rise exactly 8 in, the number is 6.75. Other brick sizes give different counts.
How many bricks are in a square meter?
A 215 × 65 mm brick with 10 mm joints takes up 225 × 75 mm, or 0.016875 m². So a square meter holds 59.26 bricks. That's why 60 bricks per square meter is the usual rule for a half-brick wall.
How much mortar do I need for bricks?
For the defaults, it's about 0.055 ft³ per square foot of wall in US units, or about 0.018 m³ (18 liters) per square meter in metric, before waste. Thicker joints and deeper bricks need more, and the calculator accounts for that.
Should I use the nominal or actual brick size?
Use the actual size here, because the calculator adds the joint itself. The nominal size is the brick plus one joint, used for planning. If you only know the nominal size, subtract one joint from the length and height to get the actual size.
How this calculator is checked
Method: Unit count = wall area ÷ ((length + joint) × (height + joint)); mortar = depth × (face with joint − brick face) per brick. Derived from the wall geometry. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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