Build your wall with confidence.
Standard 8"×8"×16" cinder blocks, also called CMU (Concrete Masonry Units). Enter your wall dimensions and get the exact block count, plus mortar bags needed.
Enter Project Dimensions
Project Diagram
Blocks Needed (incl. 10% waste)
Enter dimensions above
Mortar Bags Needed
~1 bag per 30 blocks
Recommended Depths for Cinder Blocks
| Project / Use Case | Recommended Depth |
|---|---|
| Garden Retaining Wall (1 block high) | 8 inches tall |
| Raised Bed Wall (2 blocks) | 16 inches tall |
| Standard 8ft Wall | 12 courses high |
| Foundation / Basement | Varies — use structural engineer |
How to Calculate Cinder Blocks Volume
Standard CMU blocks are 8"×8"×16". To calculate block count, divide your wall area (in sq ft) by the face area of one block (0.889 sq ft), then multiply by 1.10 for a 10% waste factor.
Each bag of mortar covers approximately 25–35 blocks. Our calculator includes the industry-standard 10% waste factor automatically.
Pro Tips for Cinder Blocks Projects
Standard CMU blocks are 8"×8"×16" (height × width × length). Always include a 10% waste factor for cuts and breakage.
One bag of mortar mix (80 lb) covers approximately 25–35 standard CMU blocks.
For retaining walls over 2 feet tall, always consult a structural engineer — wall failure can be catastrophic.