How to Measure Your Room for Carpet (Beginners Guide)

Measuring a room for carpet isn't rocket science, but getting it wrong can be costly. If you order too little, you're stuck. If you order too much, you're wasting money. Here is the foolproof way to measure a standard room.

Step 1: Draw a sketch. It doesn't need to be professional art; a simple 'birds-eye' view on a piece of scrap paper is enough. Draw the approximate shape of the floor and mark where the main door is, any windows (especially bay windows), alcoves, and if there are any built-in cupboards or fireplaces. This sketch will be your reference as you measure.

Step 2: Measure the length and width. Measure the absolute maximum length and width of the room. You must measure into the deepest part of any alcove or window recess and extend to the opposite wall. Don't forget doorways—measure right into the door frame (the 'threshold') where the carpet will meet the adjacent room's flooring. If your room is L-shaped, treat it as two rectangles and measure the 'outer' dimensions first.

Step 3: Add 10cm (4 inches) of waste. This is the single most important rule in carpet measuring. Skirting boards are rarely perfectly straight, and professional fitters need 'scribing' allowance to tuck the carpet perfectly against the wall and into corners. If your room measures 3.82m x 4.15m, you should record it as 3.92m x 4.25m. This small buffer prevents a disaster during the fitting process.

Step 4: Understand carpet widths. Carpets in the UK typically come in standard widths of 4 metres and 5 metres. Some specialized ranges also offer 1m, 2m, or 3m widths for narrow hallways. If your room width (including the 10cm allowance) is 3.8m, a 4m roll fits perfectly with minimal waste. If it is 4.1m, you will unfortunately need to jump up to a 5m wide roll to avoid a join. We generally advise against joining carpets for DIY projects as the seams can be visible if not handled by an expertMaster Fitter.

Step 5: Consider the subfloor. While you are measuring, take a look at what is beneath your current carpet. Are you on concrete or floorboards? Are there any squeaky boards that need fixing before the new carpet goes down? Do you need new underlay? A high-quality underlay can double the life of your carpet and is usually 8mm to 11mm thick, which can affect door clearances. If you are unsure, it is always best to let a professional inspect during a home visit.

Step 6: Hallways and Stairs. These are notoriously difficult to measure accurately due to 'winders' (stair treads that curve) and complex landing shapes. For these areas, we strongly recommend booking our free 'Mobile Home Visit' service in West Sussex. Our fitters can calculate the exact linear meterage required, often saving you money by utilizing offcuts from the main rooms to fit smaller landings.