Retaining Wall Calculator
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How to Use This Retaining Wall Calculator
Building a retaining wall requires precise material estimates to avoid costly trips to the supply store. This free retaining wall block calculator helps you determine exactly how many standard retaining wall blocks, capstones, and tons of drainage gravel you need for your project.
Key Features:
- Automatic Waste Factor: We include a 5% safety margin for broken blocks and cuts, so you don’t run out.
- Gravel Estimation: Most calculators forget drainage. We calculate the tons of backfill gravel required to keep your wall stable.
- Cap Stones: Calculates the finishing top row separately.
Common Retaining Wall Questions
How high can I build a retaining wall without a permit?
In most municipalities, you can build a retaining wall up to 4 feet (48 inches) without a permit. However, always check your local building codes. Walls taller than 4 feet usually require an engineer’s stamp and geogrid reinforcement.
What size are standard retaining wall blocks?
The most common garden wall blocks are 12″ wide x 4″ high. Larger structural blocks can be 16″ or 18″ wide. Our calculator allows you to select “Small,” “Medium,” or “Large” blocks to get the most accurate count.
Do I really need drainage gravel?
Yes. Water pressure (hydrostatic pressure) is the #1 reason retaining walls fail. You must place at least 12 inches of gravel behind the wall and use a perforated drain pipe with a filter sock at the base to ensure water can escape.