Retaining Wall Calculator
Calculate the number of blocks, cap stones, base gravel, and backfill material needed for a retaining wall project. Enter the wall dimensions and block size to get accurate material estimates.
Published by:
isCalculator Editorial Team
Was this calculator helpful?
How to use this tool?
How to Use the Retaining Wall Calculator
- Enter Wall Dimensions (in feet): Provide the Wall Length and Wall Height.
- Enter Block Dimensions (in inches): Specify the Block Length, Block Height, and Block Depth (defaults: 16×8×12 inches).
- Enter Cap Length (in inches): Usually the same as the block length (default: 16 inches).
- Click “Calculate Materials” – The form validates all inputs must be positive numbers.
- View Results – The calculator shows:
- Blocks – Total number of blocks needed (rounded up).
- Caps – Number of cap stones for the top row (rounded up).
- Base Gravel – Volume in cubic yards for the 6-inch gravel base.
- Backfill – Volume in cubic yards for material behind the wall (excluding the base).
Important Notes:
- All measurements must be in imperial units (feet for wall, inches for blocks).
- The calculator assumes a standard 6-inch (0.5 ft) gravel base depth and a 6-inch setback for backfill.
- Results are estimates – always add a small waste factor for your project.
Previous Results
| Result | Inputs | Date |
|---|
Frequently Asked Questions
Measure the length and height of the wall in feet. Also measure the dimensions of the block you plan to use (length, height, depth in inches). The calculator uses these to estimate materials.
Base gravel provides a stable foundation for the retaining wall. Typically a 6-inch (0.5 ft) layer of compacted gravel is placed under the wall. The calculator estimates the volume needed in cubic yards.
Backfill is placed behind the wall to aid drainage and reduce pressure. The calculator assumes backfill depth equal to block depth and height from 6 inches below top to base.