Retaining wall quantity calculator
Estimate retaining-wall blocks, cap pieces and backfill from length and height; a 6 m wall 1 m high in 0.4 × 0.2 m blocks needs 75 blocks before waste.
- Runs in your browser
- No upload
- Instant result
Quantity estimate only. This does not approve structural safety, load capacity, drainage, fire resistance or building-code compliance. Verify the design and local requirements with a qualified professional. Purchase quantities round up to whole packs.
Assumptions & formula
Formula and assumptions
w = Waste allowance/100; N=ceil(ceil(L/b)ceil(H/h)(1+w)); V=LWD(1+w); caps=ceil((L/c)(1+w))
The prefilled values are editable examples, not product specifications. Enter your supplier’s yield, density, coverage and packaging values, and add an allowance for overlaps, compaction and cuts where needed.
Purchase counts use the exact entered decimals and unit factors, without a rounding tolerance that could discard a real remainder. π and irrational square roots use enclosing bounds; ambiguous counts produce an error. Counts must be safe integers.
Results
Enter values and press Calculate to see the result here.
How to use this calculator
- Set inputs and units
Enter the wall length and height, the block face size, the cap length and the base and drainage cross-sections, and set an allowance.
- Calculate
Check this worked example: wall8×1 m,block0.4×0.2 m,cap0.4 m,base0.6×0.15 m,drain0.3×1 m,waste0% →courses5,blocks100,caps20,base0.72 m³,drainage2.4 m³
- Results
Courses and blocks per course are rounded separately. The volume entries describe the cross-sections you choose, not recommended dimensions.
Questions and limits
Does the calculator approve the wall’s stability?
No. Soil pressure, surcharge, batter, reinforcement and drainage design need competent engineering for your site.
Which input errors should I correct?
All block and cap dimensions must be positive. Mixing units, or confusing block depth with face height, distorts the courses.
What does this calculation leave out?
A quantity model for a straight rectangular wall. No geogrid, footing adequacy, curved layout or building-permit determination.