Net masonry coverage and block order
The purchase count includes your allowance and rounds upward. The unrounded quantity shows the area calculation separately. Openings remove wall coverage; it does not count lintels, bond beam units, or reinforced cores.
If the wall uses clay bricks instead of concrete blocks, the Brick Calculator estimates the separate masonry unit coverage.
The formula
Nominal dimensions include the intended mortar joint module. Area division produces a theoretical unit count; waste is applied before rounding the order to whole blocks. Use one face size for each calculation and combine separate wall sections afterward.
Worked example
A 20 ft by 8 ft wall has 160 ft² of face area. Nominal 16 in by 8 in blocks cover 0.888889 ft² each, requiring 180 units before waste. A 5% allowance increases the order to 189 blocks.
How to use this calculator
- Measure wall length and height in feet.
- Subtract the combined area of openings and enter nominal block face dimensions in inches.
- Set the waste percentage and review the whole-block order.
Choose the nominal module
A block described as 8 by 8 by 16 inches usually has smaller actual dimensions to leave room for joints. Enter the nominal face length and height for an area estimate. Using the smaller actual face without adding joints can inflate the order. Different architectural sizes and special units should be estimated from their own specified modules.
Review courses and special pieces
An area total does not describe where every piece fits. Check wall length, course height, corner returns, control joints, and openings against drawings. Partial courses and cuts can change waste. Count corner units, lintel units, caps, and bond beam units separately rather than treating every position as an interchangeable standard block.
Assumptions & limitations
What this calculation assumes
- The wall uses a uniform nominal face module.
What to keep in mind
- Excludes structural design, grout, reinforcement, and mortar quantities.
Common questions
Do I enter actual or nominal block dimensions?
Use nominal dimensions that include the joint module. Verify the specified size with the supplier.
Can I subtract every window area?
Subtract actual wall openings once. Small cuts around openings may still require additional blocks, so review the allowance.
Does this count hollow-core grout?
No. Block face coverage does not determine core volume. Estimate grout using the specified units and reinforced cells separately.
Sources & further reading
Reviewed on