How to measure toilet set-out in Australia (S-trap vs P-trap) and avoid buying the wrong suite

If you get one thing right before ordering a toilet, make it this. Toilet set-out is the measurement that decides whether the pan lines up cleanly with your outlet. Get it wrong and even the nicest toilet becomes a problem.

If you haven’t already, read our trap-type explainer first so you know what you’re measuring for.

When you’re ready to browse after measuring, start with toilets.

What is toilet set-out?

Set-out is the key distance between your finished wall or floor and the centre of the waste outlet connection point.

Simple idea, big consequences:

  • Correct set-out: toilet sits where it should.
  • Wrong set-out: awkward fit, adaptors, extra labour, or it won’t install.

Pro tip

Measure from finished surfaces only. Finished wall means tiles, not studs or bare sheeting. Finished floor means tiles, not screed or subfloor.

Before you measure: use finished surfaces

This is where DIYers get caught during renos.

  • Measure from the finished wall (tiles, not studs or bare sheeting).
  • Measure from the finished floor (tiles, not screed or subfloor).

A tile build-up of roughly 10 to 12 mm can be enough to throw your measurement out and make a set-out feel almost right but not actually right.

Tools you’ll need

  • Tape measure.
  • Torch (you’re looking behind porcelain).
  • Phone camera (take a photo for reference).
  • Optional: a second person to read the tape.

Step 1: Identify your trap type

Use these quick visual cues:

  • S-trap: outlet goes into the floor. Look for the pipe disappearing into the tiles.
  • P-trap: outlet goes into the wall. Look for the pipe going straight back into the wall.
  • Skew trap: outlet is offset left or right. If you suspect skew, confirm left-hand or right-hand as you face the toilet.

If you’re still unsure, pause and double-check before measuring.

Step 2: Measure S-trap set-out (horizontal)

For an S-trap, set-out is a horizontal measurement from the wall to the floor outlet centre.

How to measure it

  1. Stand to the side of the toilet and locate where the waste outlet goes into the floor.
  2. Find the centre point of the outlet (your torch and phone camera help here).
  3. Measure from the finished wall behind the toilet to the centre of the floor outlet.

A quick benchmark (do not use this instead of measuring)

Many Australian S-trap installs land around 140 mm set-out, and a lot of common suites cover typical S-trap ranges like 90 to 160 mm. If you measure something way outside that, treat it as a red flag and re-check your centre point and finished surfaces.

Common S-trap mistakes

  • Measuring from skirting instead of the finished wall line.
  • Measuring from studs during a reno before tiling.
  • Measuring to the edge of the hole instead of the centre.
  • Measuring a toilet that is already sitting forward on an old adaptor.

Step 3: Measure P-trap set-out (vertical)

For a P-trap, set-out is a vertical measurement from the floor to the wall outlet centre. This is where people go wrong because they hunt for a horizontal number like an S-trap.

How to measure it

  1. Locate the waste outlet where it disappears into the wall.
  2. Find the centre point of that outlet.
  3. Measure from the finished floor up to the centre of the wall outlet.

Heads up for wall-hung and in-wall cistern toilets

If you are buying a wall-hung or in-wall cistern toilet, set-out requirements are much stricter and often depend on the specific frame being used. Check the technical data sheet before core-drilling, framing, or tiling.

Extra important for P-traps

The outlet height from the floor can vary between brands and suites, so don’t assume P-trap is universal. Confirm the vertical measurement carefully.

Step 4: What if you have a universal (Uni-trap) toilet?

Many modern toilets use a connector or Vario bend style setup to convert the outlet and reach the floor for S-trap installs.

This gives flexibility, but it’s not magic:

  • You still want your set-out to be in the workable range.
  • You still need to measure from finished surfaces.
  • You still want the toilet to sit neatly without forcing awkward offsets.

As a practical guide, many Vario bend style connectors can bridge common S-trap set-outs in the 90 to 160 mm zone, which can open up a lot more suite options when you are replacing an older toilet.

Step 5: What if your outlet is offset (skew trap)?

If the outlet is offset left or right, a skew trap may be required. In that case:

  • Confirm whether it’s left-hand or right-hand as you face the toilet.
  • Take photos and measurements carefully.
  • Don’t assume a standard trap will pull across cleanly.

Quick checklists

S-trap set-out checklist

  • Measure from the finished wall (tiles).
  • Measure to the centre of the floor outlet.
  • Confirm the toilet isn’t sitting forward because of an old adaptor.
  • Take a photo of the outlet position.

P-trap set-out checklist

  • Measure from the finished floor (tiles).
  • Measure to the centre of the wall outlet.
  • Confirm the outlet height carefully.
  • Take a photo straight-on behind the pan if possible.

What to do with your measurement

Once you’ve got your set-out and trap type locked in, choosing the right toilet becomes simple. You can browse confidently knowing the suite will line up properly.

Start with our range of toilets.

FAQs

What is the most common toilet set-out in Australia?

Many S-trap installs are around 140 mm, but the safest approach is to measure your existing setup rather than assume a standard.

Do I measure toilet set-out from the studs or the tiles?

Measure from the finished surface. Tiles, not studs. Finished floor, not subfloor.

Why is P-trap set-out measured differently?

Because P-trap outlets connect through the wall, so the key measurement is the height from the floor to the centre of the outlet.

Can a plumber make a toilet fit if my set-out is slightly off?

Sometimes adaptors or connectors can help, but it can add cost and compromise the neatness of the install. Measuring correctly first is always cheaper.

What if I measure and I’m still not confident?

Take a couple of photos (side view, behind view if possible) and get a quick confirmation before ordering. That small step can prevent a wrong purchase.