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 waste outlet. Get it wrong and even the nicest toilet becomes a problem.

This guide explains how to measure toilet set-out in Australia, including the difference between S-trap set-out, P-trap set-out, universal connector ranges and offset skew trap situations. Once your measurements are sorted, you can compare suitable options in our range of toilets.

What Is Toilet Set-Out?

Toilet set-out is the key distance between your finished wall or finished floor and the centre of the waste outlet connection point. It sounds like a small measurement, but it controls whether the pan sits where it should, whether a connector can do its job, and whether your installer has a clean path or a headache.

Simple version:

• Correct set-out: the toilet lines up properly and sits where it is meant to.
• Wrong set-out: you may need adaptors, extra labour, a different toilet, or in the worst case, plumbing changes.

The part people miss is that set-out is measured differently depending on trap type. An S-trap toilet is measured horizontally from the finished wall to the floor waste centre. A P-trap toilet is measured vertically from the finished floor to the wall outlet centre.

S-Trap vs P-Trap Set-Out at a Glance

Before You Measure: Use Finished Surfaces

This is where a lot of renovation measurements go sideways. Your toilet does not care where the stud wall used to be. It cares where the finished tile face ends up. A tile build-up of roughly 10 to 12 mm can be enough to make a set-out feel almost right but not actually right.

• For S-trap toilets, measure from the finished wall. That means the face of the tiles or finished lining behind the toilet.
• For P-trap toilets, measure from the finished floor. That means the finished floor level, including tiles.
• Do not measure from skirting, studs, screed or bare sheeting. Those numbers can lead you straight to the wrong toilet.

If the bathroom is mid-renovation and the tiles are not on yet, factor that in before locking in the toilet. Better still, confirm the planned finished wall and floor build-up with the installer.

Tools You Will Need

• Tape measure
• Torch, because you are usually looking behind porcelain
• Phone camera, so you can zoom in and keep a record
• Optional second person to hold or read the tape

Step 1: Identify Your Trap Type

Before measuring, confirm what kind of outlet you actually have. Trap type tells you which direction the waste travels and which measurement matters.

Quick Visual Cues

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

If you are not sure what you are looking at, pause before buying. Trap type and set-out work together. Getting one right and the other wrong still leaves you with a toilet that may not suit the room.

Step 2: Measure S-Trap Set-Out

For an S-trap toilet, set-out is a horizontal measurement from the finished wall to the centre of the floor outlet. This is the number many Australian toilet buyers are chasing when they talk about set-out.

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, not the front or back edge of the hole.
3. Measure from the finished wall behind the toilet to the centre of the floor outlet.
4. Take a photo with the tape in place so you have a reference when comparing products.

A Quick Benchmark

Many Australian S-trap installs land around 140 mm set-out, and a lot of common toilet suites cover typical S-trap ranges such as 90 to 160 mm. Treat that as a rough benchmark only, not a replacement for measuring.

If you measure something way outside that zone, re-check the centre point, the finished wall line and whether the existing toilet is already sitting forward on an old adaptor.

Common S-Trap Measuring Mistakes

• Measuring from skirting instead of the finished wall line
• Measuring from studs during a renovation before tiling
• Measuring to the edge of the outlet instead of the centre
• Measuring the current pan position rather than the actual waste outlet centre
• Ignoring an old adaptor that may already be shifting the toilet forward

Step 3: Measure P-Trap Set-Out

For a P-trap toilet, set-out is a vertical measurement from the finished floor to the centre of the wall outlet. This is where people get caught, because they look for the same horizontal number used on an S-trap toilet.

How to Measure It

1. Locate the waste outlet where it disappears into the wall behind the toilet.
2. Find the centre point of that wall outlet.
3. Measure from the finished floor up to the centre of the wall outlet.
4. Compare that measurement against the toilet specification sheet before ordering.

Why P-Trap Needs Extra Care

The outlet height from the floor can vary between brands and suites, so do not assume P-trap means universal. A toilet can be described as P-trap and still not match your wall outlet height cleanly.

This matters even more if you are choosing a back-to-wall suite, wall-hung toilet, wall-faced pan with an in-wall cistern, or anything that needs a very neat finish. The more streamlined the toilet looks, the less forgiveness you usually have for rough measurements.

Step 4: What If You Have a Universal or 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 installations. This gives you flexibility, especially in replacement jobs where the old set-out is not perfectly matched to a new pan.

That flexibility is useful, but it is not magic:

• You still need your set-out to be within the workable range of the connector.
• You still measure from finished surfaces.
• You still want the toilet to sit neatly without forcing awkward offsets.
• You still need to check projection so the pan does not push too far into the room.

As a practical guide, many Vario bend style connectors can bridge common S-trap set-outs in the 90 to 160 mm zone. That can open up more toilet options when replacing an older suite, but the product's own specification sheet is still the final authority.

Connector Flexibility Comparison

Step 5: What If Your Outlet Is Offset?

If the outlet is offset left or right, you may be dealing with a skew trap. This is less common than standard S-trap and P-trap setups, but it matters because a standard toilet may not pull across cleanly.

If you suspect a skew trap:

• Confirm whether it is left-hand or right-hand as you face the toilet.
• Take clear photos of the outlet position.
• Measure carefully from finished surfaces.
• Do not assume a standard trap connector will solve it neatly.
• Check the product specifications or ask before ordering.

Skew trap replacement is one of those situations where a quick photo can save a lot of mucking around. A side photo, a rear photo and a measurement photo are far more useful than guessing from memory.

Quick Toilet Set-Out Checklists

S-Trap Set-Out Checklist

• Confirm the outlet goes into the floor.
• Measure from the finished wall, not skirting, studs or bare sheeting.
• Measure to the centre of the floor outlet.
• Check whether the existing toilet is already sitting forward on an adaptor.
• Take a photo with the tape in place.
• Compare the number to the toilet's set-out range before ordering.

P-Trap Set-Out Checklist

• Confirm the outlet goes into the wall.
• Measure from the finished floor, not the subfloor or screed.
• Measure to the centre of the wall outlet.
• Confirm the outlet height against the toilet specification sheet.
• Take a straight-on photo behind the pan if possible.
• Be extra careful with wall-faced, wall-hung or in-wall cistern setups.

Before You Order

• Trap type confirmed
• Set-out measured from finished surfaces
• Outlet centre measured, not edge
• Projection checked against doors, vanities and walkways
• Water inlet position checked
• Photos taken for reference
• Product spec sheet checked

What to Do with Your Measurement

Once you have the trap type and set-out locked in, choosing the right toilet becomes much simpler. You are no longer just shopping by shape or price. You are filtering out suites that will not physically suit the room.

From there, you can decide whether you want a simple close coupled replacement, a cleaner back-to-wall toilet, or a full renovation wall-hung setup. The measurement tells you what is realistic before the style conversation takes over.

Use your measurements to compare suitable options across our main toilet categories:

• Toilets
• Close coupled toilets
• Back-to-wall toilets
• Wall-hung toilets

Frequently Asked Questions

What is toilet set-out?

Toilet set-out is the distance from a finished wall or finished floor to the centre of the waste outlet connection point. For S-trap toilets, it is measured horizontally from the finished wall to the floor waste centre. For P-trap toilets, it is measured vertically from the finished floor to the wall waste centre.

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

Many Australian S-trap toilet installations are around 140 mm, but you should always measure your own bathroom rather than assume a standard. Older homes, renovations and adaptor fittings can all change the real set-out.

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

Measure from finished surfaces only. For S-trap toilets, measure from the finished wall, including tiles, to the centre of the floor waste. For P-trap toilets, measure from the finished floor, including tiles, to the centre of the wall outlet.

How do I measure S-trap toilet set-out?

For an S-trap toilet, measure horizontally from the finished wall behind the toilet to the centre of the waste outlet in the floor. Do not measure to the edge of the hole, and do not measure from skirting or unfinished wall framing.

How do I measure P-trap toilet set-out?

For a P-trap toilet, measure vertically from the finished floor to the centre of the waste outlet in the wall. P-trap set-out is not the same horizontal wall-to-floor measurement used for S-trap toilets.

Can a plumber make a toilet fit if the set-out is slightly wrong?

Sometimes connectors, adaptors or Vario bend style fittings can help, especially with some S-trap toilets. But they have limits, can add labour, and may affect how neatly the toilet sits. Measuring correctly before ordering is still the safest option.

What should I do if my toilet outlet is offset to the left or right?

If the outlet is offset left or right, you may have a skew trap setup. Confirm whether it is left-hand or right-hand as you face the toilet, take photos, and check the product specifications carefully before ordering a replacement suite.

More Toilet Buying Guides

If you are still working through the right toilet setup, these guides cover the other decisions that usually come up before ordering.

• Toilet Buying Guide Australia
• S-Trap vs P-Trap vs Skew Trap Toilets
• Toilet Seat Replacement Guide
• Replacing a Toilet Without Moving Plumbing
• Back-to-Wall vs Close Coupled vs Wall-Hung Toilets