How to Measure a Room in Square Metres (UK Guide)

Quick answer: To measure a room in square metres, measure the length and the width in metres at floor level and multiply them. A room 4.2 m long and 3.6 m wide is 4.2 × 3.6 = 15.12 m². For L-shaped or irregular rooms, split the floor into rectangles, work out each one and add them together.

Floor area in square metres is the number you need for flooring quotes, paint and heating calculations, and for checking an estate agent’s floor plan. This guide covers simple rooms, awkward shapes, bays and chimney breasts, and converting from feet. It is one of the home measuring guides on this site; for whole-property measurement, see the area and property measurement hub.

Table of Contents

What do you need to measure a room?

A tape measure of at least 5 m, ideally 8 m, with a metric scale. A laser distance measurer is quicker in large or cluttered rooms.
Paper and pencil, or squared paper, to sketch the room and write each dimension where it belongs.
A calculator, or the area calculator further down this page.
A helper to hold the end of the tape across longer runs, if one is available.

How do you measure a room in square metres step by step?

Sketch the room, measure each wall at floor level, then multiply length by width. The steps below work for any rectangular room and form the basis for every other shape.

Draw a rough plan. Mark doors, windows, alcoves and anything that juts into the room. It does not need to be to scale.
Measure the length. Run the tape along the floor from wall to wall at the longest point, keeping it straight and tight. Read it in metres to two decimal places (centimetre precision), for example 4.23 m.
Measure the width. Do the same across the room at right angles to the length.
Measure again at the other end. Walls in older UK houses are rarely perfectly parallel. If the two readings differ, note both; for buying materials use the larger one.
Multiply. Length × width = area in m². For 4.23 m × 3.58 m the area is 15.1434 m², which you can round to 15.14 m².
Write the answer on your sketch. Keep the plan; you will want it again for flooring, skirting or furniture.

If you are not confident reading the smaller divisions on a tape, the guide to reading a tape measure explains the metric and imperial markings.

Room area calculator

m× m=15.12 m² (162.8 sq ft)

How do you work out the area of an L-shaped room?

Divide the room into two rectangles, find the area of each, and add them. It does not matter where you draw the dividing line, as long as every part of the floor ends up in exactly one rectangle.

An L-shaped room split into rectangles A and B. Both methods, adding the parts or subtracting the missing corner, give 19.08 m².

There is a second way to check your answer. Measure the full outer rectangle as if the corner were not missing (5.4 m × 4.2 m = 22.68 m²), then subtract the missing piece (2.0 m × 1.8 m = 3.60 m²). The result, 19.08 m², should match. If the two methods disagree, one of your measurements is wrong.

How do you measure a room with a bay window or chimney breast?

Treat the main room as a rectangle, add the bay as a separate shape and subtract anything that takes up floor space. Victorian and Edwardian terraces often have both, so this comes up a lot in UK homes.

A splayed bay is a trapezoid: average the two parallel widths and multiply by the depth. The chimney breast footprint is subtracted from the main rectangle.

Splayed bay (angled sides): area = (width at the wall + width at the front) ÷ 2 × depth.
Square bay: a simple rectangle, width × depth.
Curved bay: if it is roughly a half circle, area = 3.1416 × radius × radius ÷ 2. A curved bay 2.0 m across has a radius of 1.0 m, so about 1.57 m².
Triangle (a corner cut across): area = base × height ÷ 2.

Whether you subtract a chimney breast depends on why you are measuring. For floor area and flooring, leave it out because nothing goes under it. For wall areas, such as working out how many rolls of paper you need, the sides of the breast add wall surface; the guide on measuring for wallpaper covers that.

How do you convert a room measured in feet to square metres?

Convert each dimension to metres first, then multiply; or multiply in feet and then multiply the square feet by 0.0929. One square foot is exactly 0.09290304 m², and one square metre is about 10.764 sq ft.

Worked example: a bedroom described as 12 ft × 10 ft is 120 sq ft. Multiply by 0.09290304 and you get 11.15 m². Converting first gives the same answer: 12 ft is 3.6576 m, 10 ft is 3.048 m, and 3.6576 × 3.048 = 11.15 m². The one thing you must not do is divide square feet by 3.28; that factor works for lengths, not areas. The site’s area converter handles other units such as square yards and acres.

Room size chart: metres to square metres and square feet

A 3 m × 3 m room is 9 m², or about 96.9 sq ft. The table gives the area for some typical room dimensions so you can sense-check your own figures.

Room dimensions	Area (m²)	Area (sq ft)
2.4 m × 2.7 m	6.48 m²	69.8 sq ft
2.7 m × 3.0 m	8.10 m²	87.2 sq ft
3.0 m × 3.0 m	9.00 m²	96.9 sq ft
3.0 m × 3.6 m	10.80 m²	116.3 sq ft
3.3 m × 3.9 m	12.87 m²	138.5 sq ft
3.6 m × 4.2 m	15.12 m²	162.8 sq ft
4.0 m × 4.5 m	18.00 m²	193.8 sq ft
4.0 m × 5.0 m	20.00 m²	215.3 sq ft
4.5 m × 6.0 m	27.00 m²	290.6 sq ft
5.0 m × 7.0 m	35.00 m²	376.7 sq ft

What counts as floor area in UK housing standards?

The government’s Nationally Described Space Standard measures floor area between the inside faces of the walls, and leaves out areas with less than 1.5 m of headroom unless they are used only for storage. The standard is used by many planning authorities in England to set minimum sizes for new homes.

It also sets minimum bedroom sizes, which are useful benchmarks when you are comparing listings:

Room type	Minimum floor area	Minimum width
Single bedroom	7.5 m² (about 80.7 sq ft)	2.15 m
Double or twin bedroom (main)	11.5 m² (about 123.8 sq ft)	2.75 m
Other double or twin bedrooms	11.5 m² (about 123.8 sq ft)	2.55 m

The same rule about headroom is worth remembering in loft rooms. If you are measuring a room with a sloping ceiling, mark where the ceiling drops to 1.5 m and measure the floor area inside that line separately from the low strips at the edges.

Common mistakes to avoid

Mixing centimetres and metres. 420 cm × 360 cm gives 151,200 cm², not 151.2 m². Convert to metres before multiplying (4.2 × 3.6 = 15.12 m²).
Measuring at skirting height or above. Furniture and skirting boards push the tape off line. Measure at floor level, from wall face to wall face.
Letting the tape sag. A sagging tape over a long run reads longer than the true distance. Keep it taut or use a laser measure.
Forgetting door recesses and alcoves. If flooring is going through to the threshold, include the recess as its own small rectangle.
Ordering materials to the exact area. The floor area is what the room measures, not what you should buy. Flooring, carpet and tiles all need an allowance for cutting and waste on top.

Frequently asked questions

How do I calculate square metres of a room?

Multiply the length of the room in metres by its width in metres. A room 5 m long and 4 m wide is 20 m².

How many square feet are in a square metre?

One square metre is about 10.764 square feet. To go the other way, one square foot is exactly 0.09290304 m².

What is the area of a 12 x 12 ft room in square metres?

A 12 ft × 12 ft room is 144 sq ft, which is about 13.38 m² (144 × 0.09290304 = 13.378).

Should I subtract kitchen units or a fitted wardrobe?

For flooring, subtract only what is permanently fixed and will not have flooring underneath, such as a chimney breast or a built-in plinth. For a room’s floor area in housing terms, fitted cupboards are usually included.

How accurate do room measurements need to be?

To the nearest centimetre is enough for almost every home job. Round each dimension up rather than down if you are buying materials.

Sources

GOV.UK: Technical housing standards, nationally described space standard
Weights and Measures Act 1985, Schedule 1 (definitions of the foot and yard)
National Physical Laboratory (NPL)