How to Measure a Toilet for Replacement: A Complete Guide

Thinking about upgrading your old toilet but not sure if a new one will fit? Measuring your toilet correctly is a crucial first step in choosing the right replacement. Whether you're tackling a bathroom renovation or simply replacing a worn-out fixture, getting the measurements right can save you time, money, and stress.

At Bathroom HQ, we’re here to guide you through the process step-by-step — and if you’re ever in doubt, our expert team is just a phone call or email away.

Why Accurate Toilet Measurements Matter

Toilets come in a variety of styles and sizes. Choosing one without checking your plumbing setup and space can lead to installation headaches — or worse, a return trip to the store. By taking a few key measurements, you’ll ensure a smooth, stress-free replacement.

Step 1: Identify the Trap Type

The trap is the bend in the pipe that carries waste away from your toilet. In Australia, the three most common types are:

• S-Trap: Waste outlet connects to the floor.

• P-Trap: Waste outlet connects to the wall.

• Skew Trap: Waste outlet runs to the side (less common, often found in older homes).

Why it matters: Your new toilet must match your existing trap type, or you'll need a plumber to make modifications.

Step 2: Measure the Set-Out

The set-out is the distance from the wall (not the skirting board) to the centre of the waste outlet.

• For S-Trap toilets, measure from the wall to the centre of the floor waste pipe.

• For P-Trap toilets, measure from the floor to the centre of the waste outlet in the wall.

💡 Pro Tip: Most standard S-trap set-outs in Australia are around 140mm, but it can vary — always double-check before ordering.

Step 3: Check the Water Inlet Position

Toilets are connected to your water supply through an inlet valve, which can be located:

• On the bottom of the cistern (bottom inlet), or

• On the side or wall (back inlet).

Measure the distance from the inlet to the waste pipe to make sure your new toilet will line up with the existing plumbing. Some modern toilets offer universal inlets, but not all.

Step 4: Measure Clearance Around the Toilet

Even if your new toilet technically fits the space, you’ll want to ensure it’s comfortable to use. Take these clearance measurements:

• Side clearance: At least 380mm from the centre of the toilet to any wall or fixture.

• Front clearance: Minimum of 530mm in front of the toilet for legroom.

• Height: Consider whether you prefer a standard toilet (around 400mm seat height) or a comfort-height model (up to 460mm).

Step 5: Record Overall Toilet Dimensions

Measure your existing toilet’s:

• Height (floor to top of cistern)

• Width (side to side at the widest point)

• Depth (front of the bowl to the back of the cistern)

This will help you find a replacement with similar proportions — especially useful if you're working with tight spaces.

Step 6: Double-Check the Manufacturer’s Specs

Once you’ve chosen a new toilet, download the product's specification sheet. This confirms the set-out, trap type, inlet position, and overall dimensions. Compare them against your measurements before you buy.

Need Help? Contact a Professional

If you're unsure about any step in the process — or if you’re worried about getting it wrong — don’t risk a mismatch. The team at Bathroom HQ is ready to help.

📞 Call Us: 03 8870 4222
📧 Email: support@bathroomHQ.com.au

Whether you're replacing a toilet or renovating your entire bathroom, we’ll make sure you find the perfect fit for your plumbing and your style.

Shop Toilets Online with Confidence

At Bathroom HQ, we stock a wide range of high-quality toilets to suit every Australian home — including back-to-wall, close-coupled, wall-faced, and rimless designs. With expert advice and reliable service, upgrading your toilet has never been easier.