Calculate Your Project
Project Diagram
Blocks Needed (incl. 10% waste)
—Blocks
Enter dimensions above
Mortar Bags Needed
—Bags (80 lb)
~1 bag per 30 blocks
Free Cinder Blocks Calculator
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.
Cinder Blocks Reference Guide
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 & Insights
1
Standard CMU blocks are 8"×8"×16" (height × width × length). Always include a 10% waste factor for cuts and breakage.
2
One bag of mortar mix (80 lb) covers approximately 25–35 standard CMU blocks.
3
For retaining walls over 2 feet tall, always consult a structural engineer — wall failure can be catastrophic.
Frequently Asked Questions
What size is a standard cinder block?▼
A standard CMU (Concrete Masonry Unit) is 8 inches high × 8 inches wide × 16 inches long. When laid with a ⅜-inch mortar joint, the installed size becomes 8 × 8 × 16 inches nominal.
How many cinder blocks are in a pallet?▼
A standard pallet of 8×8×16 cinder blocks contains 108 blocks and weighs approximately 3,000 lbs. This covers roughly 96 square feet of wall at one block high.
How many bags of mortar do I need for cinder blocks?▼
One 80 lb bag of mortar mix will set approximately 25–35 standard CMU blocks, depending on joint thickness. Factor 1 bag per 30 blocks as a planning estimate.
What is the difference between cinder blocks and concrete blocks?▼
Cinder blocks (legacy term) historically used coal cinders as aggregate and were lighter but weaker. Modern CMU blocks use concrete aggregate. The terms are now used interchangeably, but today's blocks are all concrete masonry units.