Block Wall Calculator
Calculate concrete masonry blocks and mortar for your wall project. Enter wall dimensions, select block size, and subtract openings to get accurate material counts.
Part of the Concrete & Masonry calculators — see all tools in this category.
Current result
Total length of wall in feet
Wall height in feet
1.125 blocks per sq ft (includes 3/8" mortar joints)
Standard door: 21 sq ft (3x7 ft). Standard window: 12 sq ft (3x4 ft).
Number of standard doors to subtract
Number of standard windows to subtract
10% default for cuts and breakage. Use 15% for complex layouts.
Results
160 sq ft net area
Type S masonry mortar
8 ft
Block counts include 10% waste for cuts and breakage. Order mortar based on project timeline - bags have limited shelf life. Consider adding lintel blocks for door/window headers separately.
How it works and assumptions
This calculator helps contractors and masons estimate CMU blocks and mortar for masonry wall projects. Enter your wall dimensions and opening counts to get accurate material quantities.
- Enter wall length and height in feet: Measure the total length and height of your wall. For walls with sections at different heights, calculate each section separately.
- Select block size: 8x8x16 is standard for most walls. Use 12x8x16 for taller walls or structural applications. Use 8x4x16 half-high for decorative or matching purposes.
- Enter door and window counts: Standard door opening is 3x7 ft (21 sq ft) and standard window is 3x4 ft (12 sq ft). These are subtracted from the gross wall area.
- Adjust waste percentage: Default is 10% for typical projects. Increase to 15% for complex layouts with many cuts.
- Review results: See block count, mortar bags needed, and course count. Order lintel blocks and bond beam blocks separately.
Formula: Blocks = Net Area (sq ft) x Blocks Per Sq Ft x (1 + Waste %)
Frequently Asked Questions
Need to separate CMU unit count and mortar from specified core grout? Read Bricks, Mortar and Block Fill: Estimating Different Materials.
Sources and revision
Page revision: 2026-10-12