Retaining Wall Block Calculator
Accurately estimate the number of blocks and costs for your landscaping project.
Project Estimates
Total Wall Area: 0 sq. ft.
Block Face Area: 0 sq. ft.
Blocks Needed: 0
With Waste: 0
Estimated Total Cost: $0.00
How to Calculate Retaining Wall Blocks
Planning a retaining wall requires precise measurements to ensure structural stability and cost-efficiency. This calculator helps you determine the exact number of concrete blocks or stones needed for your specific wall dimensions.
The Calculation Formula
The math behind a retaining wall estimate follows these steps:
- Wall Surface Area: Multiply the length of the wall by the exposed height (Length × Height = Area).
- Block Face Area: Calculate the area of a single block's face in square feet. Since most blocks are measured in inches, use: (Width" × Height") / 144.
- Initial Block Count: Divide the Wall Area by the Block Face Area.
- Waste Allowance: Add 5-10% to account for cuts, corners, and breakage.
Real-World Example
Imagine you are building a garden wall that is 20 feet long and 2 feet high. You are using standard blocks that are 12 inches wide and 4 inches high.
- Wall Area: 20 ft × 2 ft = 40 sq. ft.
- Block Area: (12″ × 4″) / 144 = 0.33 sq. ft.
- Blocks Needed: 40 / 0.33 = 121 blocks.
- Total with 10% Waste: 121 + 12 = 133 blocks.
Important Tips for Success
- Include the Buried Row: Most retaining walls require at least half or one full course of blocks to be buried underground for stability. Add this to your height calculation.
- The Base Material: Don't forget to account for leveling sand and crushed gravel for the base trench.
- Drainage: Walls higher than 2 feet typically require perforated drainage pipe and backfill gravel behind the blocks to prevent hydrostatic pressure.
- Cap Stones: If your wall design includes a different "cap" block for the top row, subtract one row of height from your main block calculation and calculate caps separately based on the linear length.