Retaining Wall Calculator
Calculate retaining wall blocks, base material, drainage gravel, and accessories. Includes cap blocks and geogrid requirements.
How to Use This Calculator
Building a retaining wall requires careful material estimation. Beyond the blocks themselves, you need base material, drainage components, and potentially reinforcement for taller walls.
- Measure the total length of your planned retaining wall in feet.
- Determine the exposed height of the wall (not including the buried first course).
- Select your block type or enter custom block dimensions.
- Indicate whether you want cap blocks for a finished top edge.
- Enable drainage calculation for proper water management (highly recommended).
Why This Matters
Retaining walls hold back soil and prevent erosion, but they must be properly designed and built to handle the lateral pressure from the retained earth. Inadequate drainage or undersized walls can fail dramatically, causing property damage and safety hazards. Proper material estimation ensures your wall has all necessary components for long-term stability.
- Calculate exact block quantities including waste
- Determine base gravel requirements
- Include drainage materials for proper water management
- Identify when geogrid reinforcement is needed
- Estimate total project costs accurately
Worked Examples
Garden Terrace Wall
A 20-foot long, 2-foot high decorative wall using standard 12x4 blocks.
Driveway Retaining Wall
A 40-foot long, 4-foot high wall requiring full drainage system.
Hillside Terrace System
Three terraced walls: 30 ft at 3 ft, 25 ft at 2 ft, 20 ft at 2 ft.
Common Mistakes to Avoid
- Skipping the gravel base - the foundation is critical for wall stability and drainage.
- Forgetting drainage - water pressure is the number one cause of retaining wall failure.
- Building too high without engineering - walls over 4 feet need professional design.
- Not accounting for setback - most blocks require 1/4 to 1 inch setback per course.
- Underestimating materials - always add 5-10% for cuts, waste, and hidden conditions.