Retaining Wall Block, Cap & Backfill Gravel Calculator
Estimate retaining wall blocks, caps, and drainage gravel volume.
Interactive Material & Cost Estimator
HomeYardMath.com — Hardware Store Shopping List
Estimated Material Needed 20 sq ft (+10% buffer)
Net + Buffer Area 22 sq ft 20 base sq ft
Coverage Per Package 0.33 sq ft per unit (blocks)
Total Units / Packages to Buy 67 blocks
Waste Buffer Included +10% included
Estimated Project Material Cost 67 blocks
Retail Package Total $301.50 Before local sales tax
With Delivery / Bulk $391.50 Includes $90 delivery
Quick Reference Coverage Chart (Concrete & Masonry)
Instant pre-calculated material estimates for common US residential project sizes before compaction buffer:
| Typical US Project | Area | Depth | Volume | Weight | Store Bags |
|---|---|---|---|---|---|
| 20 ft Long × 2.5 ft High Retaining Wall | 20 ft × 2.5 ft | 30 inches high | 75 Blocks | 2.5 tons gravel | 75 blocks + 20 cap stones |
Engineering Formula & Material Density Constant
Total Blocks = (Wall Length × Wall Height) ÷ Face Area per Block
Calculates total masonry retaining wall blocks and linear cap stones based on standard US block dimensions.
The Importance of Drainage Gravel Behind Retaining Walls
Hydrostatic pressure from trapped rainwater is the #1 cause of retaining wall failure. Always place a 12-inch wide column of #57 washed gravel behind the wall with a perforated drain pipe.
Frequently Asked Questions
How many blocks do I need per square foot of wall?
Typically 3 standard 8" high x 12" wide blocks per square foot of wall face.
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