The Core Formula
Calculating cinder blocks is a simple two-step process once you understand the "nominal" vs "actual" dimensions. Most cinder blocks are 8"x8"x16" nominally, which includes the 3/8" mortar joint.
Standard Wall Formula
(Wall Length × Wall Height) / 0.89 = Number of Blocks
* 0.89 is the square footage of a standard 8x8x16 block including the mortar joint.
Step-by-Step Estimation
1
Measure Surface Area
Multiply the total length of the wall by the total height in feet.
2
Subtract Openings
Calculate the square footage of doors and windows and subtract it from the total.
3
Divide by Block Size
Divide your net square footage by the coverage of one block (usually 0.89).
4
Add Waste Factor
Multiply the result by 1.10 to add a 10% waste buffer.