Retaining Wall Calculator
Calculate blocks, base aggregate and geogrid for a segmental retaining wall.
About Retaining Wall Calculator
The first course is buried, so the block count always exceeds what the exposed height suggests. Walls above about 1.2 m generally need geogrid reinforcement and often engineering sign-off. Retaining wall failures are usually drainage or reinforcement failures rather than block failures, and height thresholds for engineering approval exist for exactly that reason.
Formula
Retaining Wall
Blocks = blocks per course × (exposed courses + one buried course)
- buried course
- The first course sits below grade for stability
- geogrid
- Soil reinforcement layers required as wall height increases
Worked example
With the default values below, Retaining Wall Calculator returns Blocks Required of 189. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Wall lengthminimum 0 m
- 12 m
- Exposed wall heightminimum 0.1 m
- 1.2 m
- Block lengthminimum 100 mm
- 450 mm
- Block heightminimum 50 mm
- 200 mm
- Base aggregate depthminimum 0 mm
- 150 mm
Results
- Blocks Required
- 189
- Courses Including Buried Course
- 7
- Cap Blocks
- 27
- Base Aggregate
- 2.160 t
- Geogrid Layers Recommended
- 0
Step by step
- 1Values used
- 2Retaining Wall
- 3Blocks Required= 189
- 4Courses Including Buried Course= 7
- 5Cap Blocks= 27
- 6Base Aggregate= 2.160 t
- 7Geogrid Layers Recommended= 0
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Retaining Wall calculated?
Blocks = blocks per course × (exposed courses + one buried course) The first course is buried, so the block count always exceeds what the exposed height suggests. Walls above about 1.2 m generally need geogrid reinforcement and often engineering sign-off.
Why does Retaining Wall matter?
Retaining wall failures are usually drainage or reinforcement failures rather than block failures, and height thresholds for engineering approval exist for exactly that reason.
What values do I need to enter?
This calculator takes 5 inputs: Wall length, Exposed wall height, Block length, Block height, Base aggregate depth. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.