Retaining Wall Block Calculator
Count blocks, caps, base gravel and backfill for a retaining wall.
Reviewed by James Whitfield · How we check our maths
Your values
ⓘ Live results
Results
- Blocks needed
- 180 (+10% waste: 198)
- Cap blocks
- 20
- Courses
- 9 at 20 per course
- Base gravel
- 0.37 cubic yards
- Block cost
- $693.00
Working
- 120 blocks/course x 9 courses = 180 blocks
Quick answer
Blocks = wall face area divided by the face area of one block, plus caps along the top and a compacted gravel base under the first course.
The formula
blocks = (length x height) / (block width x block height)
Worked example
Worked example
Using the values the calculator loads with.
Inputs
- Wall length20 ft
- Wall height3 ft
- Block width12 in
- Block height4 in
- Cost per block3.50 $
Result
- Blocks needed180 (+10% waste: 198)
- Cap blocks20
- Courses9 at 20 per course
- Base gravel0.37 cubic yards
- Block cost$693.00
How to use the Retaining Wall Block Calculator
- 1Measure the finished wall length and height above grade.
- 2Enter your block's face width and height from the product page.
- 3Order about 10% extra for cuts at corners and curves.
Frequently asked questions
How deep should the base course sit?
Bury roughly one block course, or 10% of wall height, on 6 inches of compacted gravel so the wall cannot slide forward.
When do I need engineering?
Most manufacturers require a design for walls over 4 feet, or any wall holding a slope, driveway or structure above it.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error