Brick Calculator
Bricks = wall area × 6.75 per ft² (modular), + 5 % waste. A 20 × 8 ft wall is 160 ft²: 1,080 bricks net, 1,134 bricks to order and 34 bags of 80 lb mortar (+15 %). Take doors and windows off first: the 5 % waste goes on the net count, not the gross wall.
Bricks to order
1,134 bricks
1,080 net + 5 % waste · modular, 6.75 per ft²
Estimate only. Check dimensions, loads and local code requirements with a qualified professional before you build.
- Wall area
- 160 ft²
- Mortar (QUIKRETE Mason Mix)
- 34 bags of 80 lb
Worked examples
A wall 20 ft long and 8 ft high, modular brick
- 20 × 8 = 160 ft²
- 160 × 6.75 = 1,080 bricks net
- 1,080 × 1.05 = 1,134 bricks to order
- 1,080 × 1.15 ÷ 37 = 33.6, so 34 bags of 80 lb mortar
Result: 1,134 bricks and 34 bags of mortar.
Checked by the automated test “brick — 20 × 8 ft wall, modular brick, 5 % waste → 1,080 net, 1,134 to order, 34 bags of mortar”.
The same wall with a 21 ft² door
- 160 − 21 = 139 ft²
- 139 × 6.75 = 938.25, so 939 bricks net
- 938.25 × 1.05 = 985.2, so 986 bricks to order
- 938.25 × 1.15 ÷ 37 = 29.2, so 30 bags
Result: 986 bricks and 30 bags of mortar.
Checked by the automated test “brick — a door of 21 ft² is taken off first: 939 net, 986 to order, 30 bags”.
How it works
Net wall area = length × height − doors and windows
Net bricks = net area × bricks per ft² × wythes
Bricks to order = net bricks × (1 + waste), rounded up
Mortar bags (80 lb) = net bricks × (1 + mortar waste) ÷ 37, rounded up
Assumptions
- Bricks per ft² come from Table 4 of BIA Technical Note 10 for modular sizes (675 modular bricks per 100 ft²). The nominal size includes the joint, so the count is the same with 3/8 and 1/2 in joints.
- Queen and king bricks: BIA Table 4 counts 550 and 455 per 100 ft², but their size varies from maker to maker: type the count for your brick.
- Waste: 5 %, the least BIA adds to the net brick count; a job with many cuts needs more.
- Mortar: QUIKRETE Mason Mix lays up to 37 standard bricks per 80 lb bag, its best yield. BIA adds 15 to 25 % to the net mortar for waste: the calculator starts at 15 %, type up to 25 in Extra mortar.
- A load-bearing or tall wall needs a design: this counts material only.
Reference table
| Wall area | Net bricks | To order (+5 %) | Mortar bags (+15 %) |
|---|---|---|---|
| 50 ft² | 338 | 355 | 11 |
| 100 ft² | 675 | 709 | 21 |
| 160 ft² | 1,080 | 1,134 | 34 |
| 200 ft² | 1,350 | 1,418 | 42 |
| 500 ft² | 3,375 | 3,544 | 105 |
Same counts with 3/8 and 1/2 in joints for modular brick (BIA Table 4). Double them for two wythes.
Before you buy
- Brick size. Check the size on the pallet tag or the maker’s sheet: a Norman or utility brick covers far more wall than a modular one.
- Openings. Measure each door and window and add them in one field; the waste is applied after.
- Mortar. Bags are counted on the net bricks, at the best yield QUIKRETE gives, plus 15 % BIA mortar waste: raise Extra mortar up to 25 % if you expect more waste.
Common mistakes
- Adding the waste before taking off the openings BIA counts the net bricks first, then adds at least 5 %: a 20 × 8 ft wall with a 21 ft² door is 939 bricks net and 986 to order, not 1,134.
- Counting the mortar without waste QUIKRETE says an 80 lb bag lays up to 37 standard bricks, so 30 bags is the best yield, a floor. BIA adds 15 to 25 % to the net mortar: 34 to 37 bags for the 20 × 8 ft wall.
- Using the modular count for a longer brick A Norman brick is 12 in long: 4.5 per ft², not 6.75. The same 160 ft² wall takes 756 Norman bricks against 1,134 modular.
- Forgetting the second wythe A double wall takes twice the brick: 2,268 for the same 20 × 8 ft wall, and 68 bags of mortar.
Frequently asked questions
How many bricks per square foot?
BIA Technical Note 10 counts 675 modular bricks per 100 ft² of wall, so 6.75 per ft², with a 3/8 or a 1/2 in joint. Norman brick is 4.5 per ft², utility 3, queen 5.5 and king 4.55.
How many bags of mortar per 1,000 bricks?
28 bags of 80 lb premixed mortar at the best yield, 32 to 34 with the BIA waste of 15 to 25 %: QUIKRETE Mason Mix lays up to 37 standard bricks per bag, and 1,000 ÷ 37 = 27.03, rounded up. The masons' rule of 8 bags per 1,000 bricks that BIA quotes counts bags of masonry cement, sand not included, and BIA calls it very rough.
How many bricks do I need?
Multiply the wall area, doors and windows taken off, by the bricks per ft² of your size, then add 5 %. A 20 × 8 ft wall with a 21 ft² door: 139 ft² × 6.75 = 939 bricks net, 986 to order.
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- Technical Note 10, Dimensioning and Estimating Brick Masonry (Table 4, waste allowance) — Brick Industry Association, accessed
- QUIKRETE Mason Mix, product data sheet (coverage: up to 37 standard bricks per 80 lb bag) — QUIKRETE, accessed