Concrete block calculator

16 × 8 in module. Block 15 5/8 × 7 5/8, joint 3/8.

Cuts and broken blocks. Starts at 0. Add some if the wall is full of openings.

Job sheet

Plumb undefined job sheet

100 sq ft net.

  • Blocks113Face 0.889 sq ft with the joint.
Plumb undefined job sheet
100 sq ft net.

Blocks: 113 (Face 0.889 sq ft with the joint.)

The module

Face area of one block, with joint, is (length + joint) × (height + joint). A 15 5/8 by 7 5/8 block and a 3/8 joint is exactly 16 by 8 inches, 0.889 square feet. One hundred square feet is 113 blocks before you break any. Subtract doors and windows from the wall before you type the area.

Mortar bags are on the mortar calculator. The footing under the wall is the concrete calculator. Brick is a different module: brick calculator.

FAQ

Is a cinder block calculator different?

Same page. A standard unit is 8×8×16 nominal. The actual block is about 15 5/8 by 7 5/8, and the 3/8 inch joint brings the module to 16 by 8. CMU is the trade name for that unit.

How much mortar?

QUIKRETE Mortar Mix says an 80 lb bag lays up to 13 standard blocks. Use the mortar calculator once you have the block count. Corners and bond beams change it. The “up to” is why you still round bags up.

Sources

  1. QUIKRETE Mortar Mix data: 80 lb bag lays up to 13 standard 8×8×16 blocks, or 37 standard bricks.