How to Measure a Room for Carpet

Measuring for carpet is straightforward, but a few details catch people out: awkward room shapes, the width of the roll, and what "wastage" really means. Get them right and you order the right amount first time. Get them wrong and you pay for carpet you can't use, or you come up short on the day.

What You'll Need

• A tape measure (at least 5m, ideally a long one for bigger rooms)
• Paper and a pencil to sketch the room
• A calculator

Step by Step: How to Measure a Room for Carpet

1. Sketch the room. Draw a rough outline, including alcoves, chimney breasts, bay windows and doorways. You'll write the measurements on the sketch.
2. Measure the longest length and widest width. Measure wall to wall at the widest and longest points, not the middle. For an L-shaped room, split it into two rectangles and measure each.
3. Include alcoves and bays. Measure any recesses or bay windows as separate rectangles and add them.
4. Include the doorway. Carpet continues under the door to the door bar, so measure to the threshold, not the door frame.
5. Add about 10cm to each dimension. This lets the fitter trim to fit around the room's edges and corners.
6. Think about the roll. Carpet comes in 4m or 5m widths. A room under 4m wide can usually be done in one piece from a 4m roll. Wider rooms may need a 5m roll, or a join.
7. Add extra for pattern. Patterned carpet needs extra length so the pattern matches across joins. Plain carpets need less.

A Worked Example

Take a bedroom that measures 3.4m by 4.2m. The floor area is 3.4 × 4.2 = 14.3m². Add 10cm to each dimension for trimming and you get 3.5m × 4.3m.

Because the room is under 4m wide, it fits across a 4m roll, so you'd buy about 4.3m of length. That's 4.3m × 4m = 17.2m² of carpet, even though the floor is only 14.3m². The extra is waste from the roll's width, and it's normal. This is why a fitter quotes from the roll you buy, not just the floor area.

Measuring Stairs

Stairs are measured differently: each step needs the tread depth plus the riser height, plus a little extra for tucking in. For a standard 13-step staircase that's roughly 6.5m of carpet length. There's a full walkthrough in our carpet stairs and landing guide, including winder steps, which take more.

Common Measuring Mistakes

• Measuring the middle of the room instead of the widest and longest points.
• Forgetting alcoves, bays and the space under the door.
• Not adding any trimming allowance.
• Ordering only the floor area, forgetting the roll width.
• Measuring the room after furniture is in, so hidden corners are missed.

From Metres to Money

Once you have your square metres, our cost calculator gives an instant price, and our carpet fitting cost guide explains what goes into a quote: carpet, underlay, fitting and extras.

Frequently Asked Questions

Areas I Cover

Based in South London, covering Surrey, Kent and Sussex with the mobile showroom: