Retaining Wall Block Calculator
Find how many blocks, caps, and materials you need to build a retaining wall. Calculates drainage, geogrid, and cost estimates.
Total length of retaining wall
Visible height above ground
Type of retaining wall block
Leave blank to calculate from height
How much wall leans back per foot of height (0-2 inches)
Geogrid provides lateral reinforcement
Proper drainage prevents water pressure buildup
Add extra for cuts and breakage
How do I calculate retaining wall blocks needed?
Determine wall length in feet, desired height in inches, and block height. Divide height by block height to get courses (rows). Divide length by block length to get blocks per course. Multiply: courses × blocks/course = total blocks. Add 10-15% wastage for cuts and breakage.
What height requires geogrid reinforcement?
Walls under 18" typically don't need geogrid if properly compacted. Walls 18-36" need geogrid every 3rd course. Walls 36-48" need geogrid every other course. Walls over 48" typically need geogrid every course and should be engineered by a professional.
Why do I need drainage behind a retaining wall?
Water is the #1 cause of retaining wall failure. Wet soil weighs 100+ lbs per cubic foot vs 80-90 lbs dry. Without drainage, water pressure pushes the wall outward. Always include 12-18" of clean gravel behind the wall with a perforated drain tile at the base.
Do I need cap blocks on top of the wall?
Yes, flat cap blocks or pvc caps finish the wall and prevent water from seeping into the cores. Caps are especially important for walls with facing - they protect the structural blocks from weather and give a clean finished look.