About this calculator
Estimate segmental retaining wall blocks, caps, base gravel, drainage stone and drain pipe for garden and landscape walls.
How it’s calculated
Courses = ceil(height ÷ block height), plus one buried course if selected. Blocks per course = ceil(length ÷ block length). The base and drainage zone are length × width × depth.
Worked example
With these inputs:
- Wall length
- 10 m
- Exposed wall height
- 900 mm
- Block face length
- 300 mm
- Block face height
- 150 mm
- Add a buried first course
- Yes
- Cap blocks on top
- Yes
- Base trench width
- 600 mm
- Base depth
- 150 mm
- Drainage zone behind wall
- 300 mm
- Waste allowance
- 5%
the result is:
- Wall blocks
- 250 blocks
- Cap blocks
- 35
- Base material
- 0.9 m³
- Drainage stone
- 3.15 m³
- Wall face area
- 9 m²
Tips from the trade
- Walls over about 1.2 m, or holding back a slope, driveway or building, usually need engineering and often geogrid.
- Drainage behind the wall is as important as the blocks. Water pressure is what pushes walls over.
- Step the base for walls running up a slope.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the Building Regulations before ordering.