Retaining wall sleeper calculator

Enter your wall length and height to get the sleepers, posts, post-hole concrete and drainage materials for a concrete or timber sleeper wall.

Your wall

Height is the exposed height above finished ground. Add a section for each straight run.

Your sleepers

Sleeper type

Post spacing (centres)

Post depth in ground

% of height

Minimum 600 mm applied

Bury the bottom sleeper below ground level

Footings and drainage

Post hole diameter

Drainage gravel width

Behind the wall

Prices (optional)

Per sleeper

Per post

Per concrete bag

Gravel per m³

Ag pipe per metre

Change the assumptions

Minimum post depth

Concrete per 20 kg bag

m³

Timber cuts allowance

Ag pipe roll length

Your order list

How many sleepers do I need?

Divide the wall height by the sleeper height to get the number of rows. A 600 mm wall with 200 mm sleepers is three rows, or four if you bury the bottom one. Then multiply the rows by the number of sleepers it takes to cover the length.

With concrete sleepers, each sleeper sits between two steel posts, so the posts go in at sleeper-length centres. Timber sleepers can span past posts, so you can space posts closer and stagger the joins.

Don't skip the drainage

Most sleeper walls that fail are pushed over by water, not soil.
Lay slotted ag pipe in a sock along the base behind the wall, falling to an outlet.
Backfill behind the wall with drainage gravel, wrapped in geotextile fabric to keep soil out.
Set posts in concrete at the right depth and let it cure before loading the wall.

These results are estimates to help you plan and order. They don't replace an engineer's design. Post sizes, depths and spacing depend on wall height, soil, drainage and anything loading the wall, so follow your sleeper manufacturer's installation guide and check your council's rules before you build.