How to Measure for a Carpet

Getting carpet measurements right is the difference between a seamless fit and an avoidable re-order. This step-by-step guide shows you exactly how to measure a room for a carpet, including awkward spaces, stairs and landing, so you can order with confidence and minimise waste.

Use this as your definitive carpet measuring reference to plan materials, understand roll widths, and avoid common pitfalls. If you’d prefer us to take care of everything, our team can visit, measure and provide an accurate quotation.

What you’ll need

Steel tape measure (5–8 m)
Notepad or graph paper (grid makes sketching easier)
Pencil and rubber
Straightedge or ruler
Phone camera (take photos of awkward corners, door bars, and stair turns)

Before you start: key concepts that impact cost

Measure the longest and widest points of each space, not just the “average” dimensions. This accounts for out-of-square walls, bay windows and alcoves.
Carpet roll widths in the UK are commonly 4 m and 5 m (some ranges also offer other widths). Choosing the right width often removes joins and reduces waste.
Leave a small trimming allowance so your fitter can tension and tuck neatly around skirtings and thresholds. Allowing a few centimetres beyond your maximum measured length/width is a practical rule.
Pile direction and pattern matching matter. Pile should run consistently through connected spaces (e.g., hall into lounge) and patterned carpets may need extra length for matching at joins.

Step 1: Sketch the space

Grab a sheet of paper and draw a simple outline of the room. Don’t aim for a perfect scale drawing, just mark key features:

Doorways and opening directions
Alcoves, wardrobes or chimney breasts
Bay windows
Radiator pipes or boxed-in areas
Thresholds to other rooms

Label each wall with a letter (A, B, C…) to keep notes tidy.

Step 2: Measure a standard rectangular room

Measure length at the longest point (include any recesses, door reveals or bay projections).
Measure width at the widest point.
Add a trimming allowance (a few centimetres) to both length and width.
Match to the best roll width (4 m or 5 m) and note the required roll length.

Example

Your lounge measures 4.78 m (L) × 3.22 m (W) at the longest/widest points.

If you choose a 4 m roll width, orient the 4 m across the 3.22 m room width (fits comfortably) and order roll length 4.80–4.85 m (your exact longest length plus allowance).
A 5 m roll width would also fit, but wastes more material across the 3.22 m span.

Tip: try to orient the roll so it reduces seams and waste while keeping pile direction consistent with adjoining spaces.

Step 3: Measure irregular rooms (L-shapes, bays, alcoves)

Treat the space as multiple rectangles:

Divide your sketch into the fewest number of rectangles that fully cover the space.
Measure each rectangle’s longest length and width (allow for recesses).
Note the maximum overall width and maximum overall length across all rectangles, this often determines whether a single piece in a 4 m or 5 m width will cover the space without a seam.
If one piece won’t cover it, plan where a join (seam) will fall. Aim to position joins:
- Away from the room’s main sightline
- Parallel to the main light source when possible
- Outside heavy footfall (e.g., not in the middle of a doorway)

Measuring bays and door reveals

For square bays, measure out to the farthest projection in both directions.
For doorways, measure into the door reveal so the carpet tucks under the threshold bar for a clean finish.

Step 4: Hall, stairs and landing (HSL)

Stairs carpets are the trickiest area of carpet measurement. Work methodically and double-check each measurement.

A) Stair Carpet terminology you’ll use

Tread: the horizontal part you step on
Riser: the vertical part between treads
Nosing: the rounded front edge of the tread
Winders: triangular steps that turn a corner
Bullnose step: the extra-wide bottom step with rounded front

B) Straight stairs (no turns)

Count the steps (exclude the top landing if it will be carpeted as part of the landing piece).
Measure one typical step:
- Tread depth (including the part to wrap under the nosing)
- Riser height (top of one tread to top of the next)
Add tread + riser (plus a small allowance for the nosing wrap) to get the drop per step.
Multiply by the number of steps to get the required strip length. The strip width equals the staircase width (edge-to-edge) unless you’re fitting a runner.

Example: Tread 250 mm + riser 180 mm + small nosing wrap = 440-460 mm per step. For 13 steps, allow 5.7-6.0 m strip length. Measure your staircase; dimensions vary.

C) Landings and half-landings

Measure the landing as a small room: longest length and width, with allowance. If your stairs meet a half-landing, measure that platform separately. Keep pile direction consistent with the stair strip (usually down the stairs).

D) Winders and turns

For winders, measure each step individually (each has a different tread width across its arc). In many installs, winders are cut from separate templated pieces for a neat wrap. Keep notes and photos for your fitter.

E) Runners

If you’re fitting a runner (wood showing on each side), decide the border reveal you want on either side, subtract twice that from the full stair width to get the runner width, then follow the same length calculation as above.

Step 5: Choosing roll width (4 m vs 5 m) and planning joins

Your goal is to minimise seams and waste while respecting pile direction and any pattern repeat.

4 m width: Often ideal for UK rooms with widths under 3.9 m.
5 m width: Helps avoid seams in large rooms or open-plan spaces with one dimension over 4 m.
Some ranges come in both widths, letting you choose the most economical option room-by-room.

How to plan joins

Keep joins straight and parallel to a wall.
Avoid placing joins through doorways or across primary walkways.
With patterned carpets, allow extra length for pattern matching at joins.

Step 6: Underlay, grippers and trims

Underlay is measured the same way as the carpet footprint (minus built-ins).
Gripper runs around the room perimeter (not across door thresholds).
Door bars/threshold trims: count how many transitions you have (e.g., lounge→hall, hall→bathroom).
For stairs, you’ll typically use a gripper on the riser and back of the tread, with underlay cut to fit each step and landing.

Step 7: Create a clean measurement sheet

For each space, record:

Room name (“Bedroom 2”)
Longest length and width (with allowance)
Preferred pile direction (arrow on your sketch)
Roll width you plan to use and roll length needed
Notes (pattern repeat, join position, door bars, radiator pipes, unusual angles)

Common mistakes (and easy fixes)

Measuring “wall to wall” once and assuming the opposite wall is identical.
- Fix: take multiple measurements and use the largest dimension.
Forgetting door reveals and bay windows.
- Fix: always include projections and recesses in your longest/ widest measurements.
Ignoring pile direction across connected spaces.
- Fix: draw arrows on your plan, align all pieces accordingly.
Placing joins in high-traffic paths.
- Fix: position joins away from main sightlines and footfall.
Underestimating stairs with winders or bullnose steps.
- Fix: measure each winder separately; photograph turns and unusual steps for templating.

Frequently Asked Questions

How to measure a room for a carpet quickly?

Sketch the room, measure the longest length and widest width, include recesses and door reveals, add a small trimming allowance, then select the most economical 4 m or 5 m roll width.

What are standard carpet widths in the UK?

Most domestic carpets are available in 4 m and 5 m widths (some lines offer additional widths). Check the specification of your chosen range.

How much extra should I add for trimming?

Allow a small margin beyond your maximum measured length and width to enable accurate fitting and tucking. Many measuring guides recommend leaving a modest allowance rather than ordering exact-to-the-millimetre.

How do I measure stairs for carpet?

Measure tread + riser (add a little for the nosing wrap). To get the drop per step, multiply by the number of steps and record the full stair width (or desired runner width). Measure landings as separate small rooms.

Should joins run a particular way?

Where possible, place joins parallel to light and away from heavy traffic. For patterned carpets, allow extra length for pattern matching along the seam.

Why measure with Colourbank?

As Leicester’s largest independent retailer for carpet, flooring and beds, Colourbank carries extensive ranges and premium underlays to suit every budget. Bring your sketches into our Leicester showroom or book a professional measure with us.

We’ll confirm quantities, advise on roll width selections to reduce seams and schedule expert fitting for a perfect finish.If you have any queries, please contact us here. Our team is happy to help.