Retaining wall calculator

Enter the wall length and height, set the block size — get block and cap counts, the compacted gravel base, the drainage backfill and the drain pipe.

isometricnot to scale

Units

Wall length

Wall height (above grade)

Block length (mm)

Block height (mm)

Include cap row

Waste allowance %

Price per block (optional)

For garden walls up to about 3–4 ft. Taller walls need engineering — surcharge loads and soil push grow fast.

Material scheduleSheet 01Retaining wall calculator

Enter the dimensions and press Calculate — the quantities appear here as a printable sheet.

📐 You need

Frequently asked questions

How deep should the base be for a retaining wall?

Dig a trench and place 4–6 in of compacted crushed gravel under the first course, and bury the first course about 10% of the wall height (minimum one block). A level, compacted base is 90% of a straight wall.

Does a retaining wall need drainage?

Yes — water pressure behind the wall is what topples it. Put 12 in of clean crushed gravel behind the blocks, a perforated drain pipe at the base sloped to daylight, and geotextile between gravel and soil.

How high can I build without an engineer?

Most block systems allow 3–4 ft (0.9–1.2 m) unreinforced with a level backfill. Above that, or with a slope or driveway pushing on the wall, you need geogrid reinforcement and an engineered design — local codes often require a permit past 4 ft.

What is the setback or batter of a retaining wall?

Segmental blocks step back into the slope, typically ¾–1 in per course, via a rear lip or pins. This lean plus the buried first course is what lets a dry-stacked wall resist soil pressure.