How to Measure for a New Bathroom Suite (With Diagrams)

Posted by Catherine Parkinson on Wednesday 30th July 2025, updated on Tuesday 5th August 2025

When planning a bathroom renovation or fitting a bathroom suite, measuring your bathroom accurately is one of the most crucial first steps. Even measuring a few millimetres off can end in complete disaster. Misaligned plumbing, awkwardly placed fixtures, expensive returns - the possibilities are endless! In short, it’s something you want to avoid. So, before you fall in love with that perfect freestanding bath or sleek wall-mounted vanity unit, you need to know if it will fit.

Our bathroom planning guide will walk you through how to measure for a bathroom suite with practical tips and helpful diagrams for visual reference. Whether you’re replacing old fixtures or starting fresh, this guide will help you avoid costly mistakes later down the line.

Why Proper Bathroom Measurements Matter

Proper measurements are essential to ensure fixtures fit comfortably without crowding the space. With so many factors to think about, including plumbing, electrical points, adequate clearance for doors, drawers, and standard building regulations (we are only scratching the surface here!), it's clear to see why bathroom layout planning accurately prevents delays, budget overruns, and design compromises later.

What This Guide Covers

Whether you're planning a bathroom renovation or starting from scratch, having accurate measurements is the foundation of a successful project. This guide is designed to walk you through the essential steps to measure your bathroom space correctly, helping you avoid expensive mistakes and ensuring everything fits as intended. Here's what this guide covers:

The tools you’ll need
What to measure and why
A step-by-step process using visual bathroom layout diagrams
Common measuring mistakes and how to avoid them

Tools You’ll Need - Be Prepared

Before pulling out your tape measure, gather these essential bathroom measurement tools together to ensure accuracy and efficiency throughout the process:

Measuring tape (at least 5 metres for full coverage)
Graph paper or digital drawing tool (e.g. SketchUp, MagicPlan)
Pencil and ruler for sketching
Spirit level (for checking floor and wall levels)
Helper (optional but useful for long measurements)

Having the right tools will make your bathroom planning checklist smoother and more precise.

Key Areas to Measure

It's time to get measuring. But before you begin, it's important to approach your bathroom methodically by breaking it down into key zones. This will help you stay organised and ensure that every element is accounted for. By focusing on one zone at a time, you can take more accurate measurements and avoid missing crucial details. Carefully recording the dimensions, locations of fixtures, and positions of plumbing and electrical points in each zone will also make the planning and installation process much smoother. Here’s how to go about it:

Room Dimensions

Measure length, width, and height of the room
Take note of any alcoves, niches, or boxed-in pipework
If there are sloped ceilings, record where the slope begins and ends

Knowing your exact bathroom dimensions ensures accurate fixture placement and ventilation planning.

Door and Window Placement

Measure width and height of doors and windows
Record clearance space needed for door swings
Note which way the door opens (inward or outward)
Measure sill height and distance from corners

These measurements help avoid obstruction when placing basins or toilets near windows or doors.

Existing Fixtures and Plumbing Points

Record the current position of the toilet, basin, bath, and shower
Measure the centre-to-wall distances (e.g., centre of toilet pan to adjacent wall)
Note the waste pipe locations (usually found behind or below each fixture, but their placement is influenced by gravity flow and building regulations)
Mark visible hot/cold water pipes and electrical sockets

Waste Pipe Location Breakdown

Basin

Location: Behind or below the basin, often embedded in or exiting the wall.
Type: 32mm or 40mm waste pipe.
Direction: Into wall cavity or floor, sloped slightly downward.
Placement Tip: Centre of waste usually 500–600mm from the floor, depending on vanity height.

Shower / Bath

Location: Beneath the shower tray or bath, often routed through the floor.
Type: 40mm or 50mm waste pipe.
Direction: Slopes slightly downward (1:40 gradient) to connect with main waste.
Placement Tip: Pipe access is usually under the tub/shower or in a nearby void

Toilet

Location: Directly behind or beneath the toilet pan.
Type: Large-diameter pipe (typically 100mm/4 inches).
Direction: Runs horizontally to the nearest soil stack or vertically into the floor.
Placement Tip: Usually about 180mm–220mm from the wall to the centre of the pipe for close-coupled toilets.

Water Pipe (Hot/Cold) Location Breakdown:

Basin:

Pipes are usually located directly beneath the sink.
They run vertically from the floor or horizontally through the wall behind the sink.
Typically 4–6 inches apart (centre to centre) for hot and cold.
Height: ~18–24 inches off the floor.

Shower/Bathtub:

Pipes are inside the wall behind the control valve.
Hot and cold lines feed the valve from below or the side.
The shower head pipe runs vertically up from the valve.

Toilet (Cold Only):

Cold water pipe comes out of the wall or floor, usually behind or just to the side of the toilet.
Height: ~6 inches from the floor.
Offset: ~6 inches to the left or right of centerline.

Understanding your plumbing layout for the bathroom is vital if you plan to keep existing plumbing or make minor adjustments.

Clearance Zones & Walkways

Clearance zones and walkways are essential for safe, comfortable, and code-compliant use. These areas ensure that fixtures like toilets, sinks, showers, and bathtubs are accessible and functional. As a general rule, the best clearance space for a bathroom suite is at least 760mm from the front of the fixture to any obstacle. Let's take a closer look at UK guidelines:

Standard Fixture Clearance Zones (UK Guidelines)

Toilet

Side clearance: Minimum 400mm (15.7in) from centreline to side wall or fixture
Front clearance: At least 600mm (23.6in) from front of toilet to obstruction
Between toilet and basin/bidet: Ideally 750mm centre-to-centre
Comfort tip: More space improves usability, especially in compact bathrooms

Basin/Vanity Unit

Front clearance: At least 600mm
Side-to-side spacing: Leave at least 500mm between basin and adjacent fixture or wall

Bath

Front clearance: 700mm minimum recommended
Side space: Not always needed, but allow 300–500mm for ease of access if possible

Shower Enclosure

Standard enclosure: Minimum 800mm x 800mm
Walk-in shower: Aim for 900mm x 900mm or more
Door swing: Leave 500mm clearance in front of door
Access zone: At least 600mm in front of opening

Walkways & Circulation

Main walkways should be at least 750mm–900mm wide
1200mm width is ideal for two-way traffic or spacious layouts

Proper fixture spacing ensures comfort and usability, avoiding a cramped and claustrophobic design.

Sources:

UK Accessible Bathroom Design (based on BS 8300-2:2018)

These are for wheelchair-accessible or accessible bathrooms, common in new builds or inclusive homes.

Toilet

Unobstructed access on one or both sides
Space: 1000mm from side wall to WC centreline (if access is only one side)
1400mm clear space in front of WC

Turning Circle

Provide a 1500mm diameter clear turning circle
Can overlap slightly with basin or clear space under basin

Level-Access Shower (Wet Room or Roll-In)

Minimum size: 1200mm x 1200mm
Preferred size: 1500mm x 1500mm for greater comfort
Slip-resistant floor
Include shower seats and grab rails

Accessible Basin

Height: 720–740 mm from floor
Clear knee space below
Lever or sensor taps for ease of use

Doorways

Minimum 850mm clear opening width
Doors should open outward (or be sliding) to avoid blocking the user inside

For more information on accessible bathroom guidance, explore the government website: Access to and use of buildings: Approved Document M - GOV.UK.

Tips for Accurate Measuring

Avoid These Common Mistakes

To make your bathroom measuring process foolproof, keep these pro tips in mind:

Double-check all measurements (once is never enough, trust us!)
Use millimetres or centimetres consistently
Account for tile thickness or wall finishes that might affect final fixture fittings
Take photos of your existing layout - this will be useful for future reference
Don’t forget vertical measurements, especially for wall-hung vanity units or sloped ceilings
If uncertain, consult with a professional designer or fitter to validate your measurements

Skipping or misreading even one measurement can derail your entire project. A little caution now saves major frustration later.

Plan with Confidence

Taking the time to properly measure for a bathroom suite is an essential first step in any successful bathroom renovation or redesign. From the basic room dimensions to complex plumbing layouts, every millimetre matters.

Use a bathroom layout diagram to visualise your space, and record everything clearly. Whether you’re working with a small ensuite or a spacious family bathroom, proper planning will lead to better results.

Finally, always check your measurements with a professional supplier or designer before ordering your new bathroom suite. With the right planning and accurate measurements, your dream bathroom can become a reality.

If you're looking for further inspiration, take a look at the following posts - How to Measure Shower Doors | A Plumbworld Guide - How to Measure A Shower Tray | A Plumbworld Guide - How to Measure for a Toilet Seat.