Block & Brick Calculator
Enter the wall length and height to find how many 8 × 8 × 16 concrete blocks or modular bricks to buy, and how much mortar mix they'll take.
Enter the wall size and the unit size.
On this page
How to use the block and brick calculator
- Measure the wall length and height. For a building or planter, add the lengths of all walls.
- Subtract openings such as doors and windows in square feet.
- Choose the unit. Standard concrete blocks have a nominal 8 × 16 in face whatever their width (4, 6, 8 or 12 in); bricks are much smaller.
How the count works
Masonry units are sold by nominal size, which includes a ⅜ in mortar joint. An 8 × 8 × 16 block is actually 7⅝ × 7⅝ × 15⅝ in, so with mortar it occupies exactly 8 × 16 in of wall.
| Unit | Nominal face | Per sq ft | Per 80 lb bag of mortar mix* |
|---|---|---|---|
| Concrete block | 8 × 16 in | 1.125 | about 12 |
| Half-high block | 4 × 16 in | 2.25 | — |
| Modular brick | 2⅔ × 8 in | 6.75 | about 37 |
*From the QUIKRETE Mortar Mix data sheet usage chart (60 lb: about 9 blocks or 28 bricks; 40 lb: about 6 blocks or 19 bricks).
Worked example: a 20 ft garden wall, 4 ft high, in 8 × 8 × 16 block
- Area: 80 sq ft × 1.125 = 90 blocks, plus 5% = 95 blocks
- Mortar: 95 ÷ 12 = 7.9 → 8 bags of 80 lb mortar mix
- Courses: 48 in ÷ 8 in = 6 rows
Things the count doesn't include
- Footing: block walls sit on a concrete footing, usually twice as wide as the wall — size it with the concrete calculator.
- Reinforcement and grout: structural and retaining block walls typically have rebar in cores filled with grout or concrete, per the design.
- Special units: corner blocks, bond beams and caps are counted separately if your design uses them.
For retaining walls, interlocking segmental blocks designed for the job are easier and usually more reliable for DIY than mortared concrete block. See the retaining wall calculator.
Frequently asked questions
How many concrete blocks per square foot?
1.125 standard 8 × 16 in blocks, or 112.5 per 100 sq ft of wall.
How many bricks per square foot?
About 6.75 modular bricks with ⅜ in joints — 675 per 100 sq ft of single-wythe wall.
How many blocks does a bag of mortar lay?
QUIKRETE lists about 12 standard 8 × 8 × 16 blocks per 80 lb bag of Mortar Mix, 9 per 60 lb bag and 6 per 40 lb bag.
Sources
- QUIKRETE, Mortar Mix (No. 1102) data sheet — usage chart for block and brick.