Calculate the number of concrete blocks or CMUs needed for a wall plus mortar requirements.
Step 1: Enter the wall length and height.
Step 2: Subtract any openings (doors, windows) by entering their total area.
Step 3: Select your block size. Standard CMU is 8×8×16 inches (nominal, actual 7⅝×7⅝×15⅝).
Results include block count, mortar bags, and grout volume if you plan to fill cores.
For standard 8×16 blocks, you need 1.125 blocks per square foot (including mortar joints). This equals about 112–113 blocks per 100 sq ft.
Not always. Structural walls and those with rebar typically require filled cores. Non-structural or garden walls often leave cores empty or fill only reinforced cells.
Plan for approximately 3 bags of 80-lb mortar mix per 100 standard blocks. This varies with joint thickness and block size.
The standard UK block is 440 × 215 mm (about 10 blocks per m²), while US CMU blocks are nominally 8 × 8 × 16 inches. Always confirm the exact block size before ordering, as coursing depends on it.
Hollow blocks are often filled (grouted) with concrete and rebar for load-bearing or retaining walls; non-structural walls are usually left hollow.
