Landscape & Groundwork
Retaining Wall Calculator
Estimate regular blocks and caps for a straight block retaining wall.
Enter your measurements
Results update as you type.
About this calculator
Enter the wall length and body height (including any buried courses you choose), the actual block face dimensions and any extra allowance. Add an optional cap length for cap blocks and an optional gravel base cross-section for a material volume. Body height excludes the cap.
How to measure
- Measure wall length and the block-body height, excluding cap height.
- Use the effective block face dimensions and cap length of the actual product.
- Enter base width and depth together if you want a gravel quantity; stability and drainage design are outside this calculator.
How to use this calculator
- Measure the straight wall length and the body height.
- Enter the actual block face dimensions.
- Add an allowance for cuts and breaks if desired.
- Optionally add cap length and gravel base dimensions.
- Calculate for blocks, caps and volume.
Formula
Columns = ⌈wall length ÷ block width⌉
Courses = ⌈body height ÷ block height⌉
Regular blocks = ⌈columns × courses × (1 + extra ÷ 100)⌉
Caps = ⌈wall length ÷ cap length⌉ when supplied
Gravel volume = wall length × base width × base depth when supplied
Assumptions
- Straight wall only; body height excludes the cap.
- Blocks are laid in whole columns and courses; partial blocks round up.
- Extra allowance applies to the body blocks, not the caps.
Common mistakes
- Counting visible face area without checking embedment and courses.
- Forgetting separate caps, corners and drainage materials.
- Treating block quantity as proof of wall stability.
Worked example
Try it: press “Load example” above the form.
A 6 m wall of 0.5 × 0.2 m blocks at 1.2 m high is 12 columns × 6 courses = 72 blocks, plus 12 caps.
Limitations
Quantity takeoff only. No wall stability, safe height, buried depth, reinforcement, drainage or geogrid specification. Curves, corners and setback patterns are unsupported.
Frequently asked questions
Does a block count prove the wall is stable?
No. Height, surcharge, soil, drainage, embedment and reinforcement determine structural requirements. The result is a simple material layout.
Are caps and drainage counted together?
Caps are counted separately where entered. Drainage aggregate, pipe, fabric, corners and reinforcement need their own quantities and product instructions.
What does the worked example show?
A 6 m wall of 0.5 × 0.2 m blocks at 1.2 m high is 12 columns × 6 courses = 72 blocks, plus 12 caps.
Which assumptions should I check before using the result?
Quantity takeoff only. No wall stability, safe height, buried depth, reinforcement, drainage or geogrid specification. Curves, corners and setback patterns are unsupported.
Sources
Sources explain the methods and any named product presets. Check your product label where coverage, yield or density differs.
- Inch Calculator: retaining wall quantities
Wall/cap quantity context. Supplier-coverage division for flagstone is the stated arithmetic method, not a universal coverage recommendation.
Calculation documentation · Updated 2026-11-08 · Version 1.6.4. Estimates are planning aids. Confirm quantities, coverage and prices with your supplier before purchasing. Found an error? Report it.
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