The formula
Wall area = length × height − doors and windows Per sq ft = 144 ÷ ((brick length + joint) × (brick height + joint)) Bricks = wall area × per sq ft × (1 + extra %) Mortar = bricks ÷ about 33 per 80 lb bag
Example: a 20 ft wall 8 ft high with a 20 sq ft door opening has 140 square feet of brick. Modular bricks with 3/8 inch joints need 6.86 per square foot, so 960 bricks, or 1,008 with 5% extra, and about 31 bags of mortar.
Quick answers for common wall areas
| Wall area | Modular bricks | 80 lb mortar bags |
|---|---|---|
| 50 sq ft | 360 | 11 |
| 100 sq ft | 720 | 22 |
| 200 sq ft | 1,440 | 44 |
| 300 sq ft | 2,160 | 66 |
| 500 sq ft | 3,600 | 110 |
| 1,000 sq ft | 7,200 | 219 |
Bricks per square foot
| Brick | Size (in) | Per square foot |
|---|---|---|
| Modular | 7⅝ × 2¼ | 6.86 |
| Queen | 9⅝ × 2¾ | 4.61 |
| King | 9⅝ × 2⅝ | 4.8 |
| Utility | 11⅝ × 3⅝ | 3 |
The count is for a wall one brick thick. A double wall takes twice as many. For concrete block walls use the concrete block calculator.
Sources and assumptions
Mortar uses about 30 to 35 standard bricks per 80 lb bag of mortar mix, as printed on common bagged mortar; change Bricks per 80 lb bag to match your bag. Brick sizes are the usual US actual sizes.
Questions
How many bricks are in a square foot?
About 6.86 modular bricks with 3/8 inch mortar joints, or 7 to allow for waste.
How many bricks can one bag of mortar lay?
An 80 lb bag of mortar mix lays roughly 30 to 35 standard bricks.
How many bricks do I need for 100 square feet?
About 720 modular bricks with 5% extra, and around 22 bags of mortar.
References and review
- Quikrete Mortar Mix: bag sizes and coverage (product page and data sheet)
- NIST Special Publication 811: unit conversion definitions
Units convert with exact definitions: 1 ft = 12 in = 0.3048 m, 1 yd³ = 27 ft³. Results round up to whole bags, sheets and pieces so you don’t come up short. Last reviewed October 19, 2026. If your bag, pallet or supplier lists a different figure, use theirs: change the matching field above.