How to calculate bricks and blocks
Masonry is estimated by wall area. Find the area, then multiply by how many units cover a square foot (mortar joints included):
Units = wall area (sq ft) × units per sq ft × (1 + waste)
Measure the wall's length × height, subtract big openings like doors and windows, and add 5–10% for breakage and cut units. The number of units per square foot depends on what you're laying:
| Unit | Nominal face (with joint) | Per sq ft |
|---|---|---|
| Modular brick | 8 × 2⅔ in | ~6.75 (about 7) |
| Concrete block (CMU) | 16 × 8 in | ~1.125 (about 1⅛) |
Don't forget the mortar
Mortar use varies with joint thickness and your technique, but a useful rule of thumb is about one 80-lb bag of mortar mix per 30 modular bricks, or per 12 standard blocks. If you mix your own with masonry cement and sand instead of a premixed bag, plan on sand too. Buy a little extra — running out mid-course is a headache.
Good to know
- This is a single-wythe wall. A wall that's two bricks thick (a double wythe) needs roughly twice the brick — run the numbers for each layer.
- Subtract real openings. Large doors and windows remove a meaningful number of units, so enter their combined area.
- Structural walls need more than a count. Load-bearing or retaining walls require proper footings, reinforcement, and often a permit — check local codes or a pro.