How to Measure Stairs for Carpet: A UK Fitter’s Step-by-Step Guide
Thinking of new carpet for your stairs? Measuring seems simple, but getting it wrong is the single most expensive DIY mistake you can make. It often costs hundreds in wasted carpet or, even worse, leaves you short on the final step.
Most online guides will tell you to measure the total square metres. This is completely wrong.
Carpet comes in fixed roll widths, typically 4 metres or 5 metres in the UK. A professional carpet fitter, like myself, doesn’t measure for area; we measure for a cutting plan. This plan maps out how each piece will be cut from that single, large roll, ensuring every step matches perfectly.
This is a professional fitter’s guide. I’ll show you exactly how to measure stairs for carpet, whether you have straight stairs, a landing, or tricky winders, just like a pro does. We will cover pile direction, roll widths, and the formulas you need to ensure you buy the right amount of carpet, save money, and get a flawless result.
The #1 Mistake: Measuring Area vs. UK Carpet Roll Width
Before we even touch a tape measure, let’s clear up the biggest myth.
Amateur guides tell you to find the square metres (sq/m) of your stairs. This is useless information for a carpet retailer or fitter. Why? Because you cannot buy a 0.9m wide, 6m long “strip” of carpet. You buy a piece cut from a 4-metre or 5-metre wide roll.
Let’s say your stairs are 0.9m wide and you need 6m in length. Your total “area” is 5.4 sq/m. But you must buy a piece that is 6m long by the 4m roll width. That’s 24 sq/m of carpet.
This is where the “cutting plan” comes in. A professional looks at the entire job. Maybe your landing is 3m x 2.5m. We know we must use a 4m roll. So, we’ll buy a 3.1m length from that 4m roll (3m + 10cm allowance).
This gives us a piece measuring 3.1m x 4m. We’ll cut the 3.1m x 2.6m (2.5m + 10cm) piece for the landing. What’s left? A large “offcut” measuring 3.1m x 1.4m.
Now, the fitter asks: “Is 1.4m wide enough for the stairs?” If your stairs are 0.9m wide, the answer is yes. “Is 3.1m long enough?” If your stairs are short, maybe. If not, we plan to use that 1.4m wide offcut for the winder steps and use a separate piece for the straight run.
This is the professional mindset. You are not just measuring stairs; you are planning a cutting map. This guide will show you how to create that map.
Before You Start: Tools & Key Term
A good fitter prepares their tools first. You don’t need much, but you do need the right things.
The Tools You’ll Need
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Metal tape measure: A good quality, 8-metre tape is best. Don’t use a “soft” tailor’s tape or a laser, as they can be inaccurate.
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Notepad & pencil: You’ll be drawing a sketch and writing down measurements.
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Calculator: Your phone is perfect for the maths.
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A helper (optional): Handy for measuring long landing drops or holding the tape steady, but not essential.
A Fitter’s Vocabulary: Tread, Riser, Nosing & Pile
To measure like a pro, you need to talk like one. Here are the only terms you need to know.
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Tread: The flat part you step on.
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Riser: The vertical part between each step.
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Nosing: The small lip of the tread that overhangs the riser. Some modern stairs don’t have this, but most UK homes do.
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Pile Direction: This is the most important term. It’s the way the carpet fibres naturally lie, and getting it wrong will ruin your project.
Pro-Tip
The Golden Rule: Always Check the Pile Direction!
This is my number one piece of advice. Carpet pile has a direction, just like stroking a cat. On stairs, the pile must run down the staircase on every single step.
Why? Light. If you turn one piece 90 degrees (or, worse, run it up the stairs), the light will hit it differently. It will look like a completely different colour, even though it was cut from the same roll. This is the most common and costly mistake a DIYer can make.
Action: Find the carpet sample. Rub your hand along it. The “smooth” direction is the way the pile lies. This direction must point down your stairs. When you get your carpet, mark the back of every single piece with a pencil arrow (e.g.,
↓) showing the pile direction before you even think about cutting.
How to Measure Straight Stairs (The Easiest Method)
This is the method for a standard, straight staircase with no turns. We will measure this as one long “strip” or “runner.”
Step 1: Measure a Single Step (The “Tread + Riser” Formula)
First, we need the length of carpet required to cover one single step.
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Measure the depth of one tread. Start from the back and measure to the very front of the nosing.
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Measure the height of one riser.
Now, add them together.
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Formula: (Tread Depth + Riser Height) = Length per step.
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Example: Your tread is 25cm, and your riser is 20cm. Your length per step is 45cm (25 + 20).
A quick note: If your steps have a prominent, rounded “bullnose,” you need to account for this. Hook your tape measure on the riser under the nosing and measure up and over the tread to the back. This gives you a more accurate “Tread + Riser” length. We’ll cover this in the “Bullnose Method” section later. For now, the simple (Tread + Riser) is fine.
Step 2: Calculate Total Length
Count the number of stairs. Now, multiply this by the length per step.
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Formula: (Length per step) x (Number of Stairs) = Total Length
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Example: 45cm per step x 13 stairs = 585cm (or 5.85 metres).
Step 3: Measure the Stair Width
This one is easy. Measure the width of a single step. Measure in a few places just in case your walls aren’t perfectly straight, and use the widest measurement.
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Example: Your stairs are 80cm wide.
Step 4: Add Your Allowance (The “Trimming Room”)
Do not order a piece that is exactly 5.85m x 0.8m. It will fail. You must add an allowance for trimming.
We always add a 10cm (4-inch) allowance to the final length and the final width.
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Why? This isn’t “waste.” This is the essential “trimming” and “tucking” room. Your fitter (or you) will use this extra material to stretch the carpet onto the gripper rods and tuck it into the edges for a tight, professional, and safe finish.
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Example Length: 5.85m becomes 5.95m.
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Example Width: 80cm becomes 90cm.
Your Final Piece: For this staircase, you need to order one “strip” of carpet measuring 5.95m x 0.9m. Your retailer will cut this from a 4m or 5m roll.
How to Measure Landings (Top, Bottom, or Half-Landings)
Landings are simple, but this is where the “roll width” concept is critical.
A landing is just a square or rectangle. You must measure the longest length and the widest width.
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Measure the longest wall of the landing.
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Measure the widest point of the landing (e.g., from the wall into a doorway).
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Add your 10cm trimming allowance to both measurements.
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Example: Your landing measures 2.2m x 3.1m. Your “purchase size” is 2.3m x 3.2m.
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Now, the crucial step: Compare your width to the standard UK roll widths.
Your landing is 3.2m wide. This means you must buy from a 4-metre roll. You cannot use a 3.2m width. You will be sold a piece that is 4m wide by 2.3m long.
This is why we measure. You’ve just identified that your “landing piece” will be 2.3m x 4m. This is the piece you (or your fitter) will use to cut your 2.3m x 3.2m landing. The “offcut” will be 2.3m x 0.8m. Can this be used for anything? Maybe for a few straight steps? This is the “cutting plan.”
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The Pro-Move: If your landing and stairs are being carpeted together, we try to plan this as one purchase. We’d map out the (2.3m x 3.2m) landing piece and the (5.95m x 0.9m) stair piece on paper. We would see if they can both be cut from one single piece, like a 6m length of a 4m roll, to minimise waste and cost.
How to Measure Winding Stairs (The Pro Method)
This is where amateurs give up and pros get to work. “Winding” or “winder” steps are the pie-shaped steps that take you around a corner.
Do not use the straight stair formula. Do not just “measure the widest part.” This will fail. You must measure every single winder step individually.
Step 1: Treat Each Winder as a Separate Box
Forget the pie shape. You are going to measure a “box” that each winder step would fit inside.
Step 2: Measure the Longest Length (Tread + Riser)
For each winder step, find its very deepest point (usually the part sweeping around the outside of the turn). Measure the tread depth at this point, and add the riser height below it.
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Example: Winder 1’s deepest point is 60cm (tread + riser).
Step 3: Measure the Widest Width
Now, for that same step, find its very widest point. This is usually from the narrowest point on the inside to the widest point on the outside.
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Example: Winder 1’s widest point is 95cm.
Step 4: Add Your 10cm Allowance
Add the 10cm (4-inch) trimming allowance to both of these measurements.
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Example: Winder 1 needs a “box” of carpet measuring 70cm x 105cm.
Now, repeat this for every single winder step.
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Winder 2 might need a 75cm x 105cm piece.
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Winder 3 might need a 65cm x 100cm piece.
[Common Mistake]
Don’t Assume Winders are Identical!
I see this all the time. A DIYer measures one winder, multiplies by three, and comes up short. It’s a guaranteed way to waste an entire carpet. In almost every UK home, each winder has a slightly different angle and width. Measure every single one. Take your notepad, draw the winder section, and write the “box” dimensions for each step.
Step 5: Sketch Your Cutting Plan
You now have your measurements. Let’s say you have 3 winders and 10 straight steps.
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3 Winder “Boxes” (e.g., 70×105, 75×105, 65×100)
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1 Straight Stair “Strip” (e.g., 4.6m x 0.9m)
You’ll draw a 4m roll on your notepad and see how you can “nest” these pieces onto it. Remember, all your pile direction arrows must point the same way!
You’ll quickly see it’s a puzzle. This is what you pay a fitter for. But with these measurements, you can go to a retailer and ask for an accurate cost estimate. You can say, “I need these four pieces, all with the pile running along the longest measurement. What is the most economical way to buy this?”
Advanced Details Fitters Never Forget
Want to be 10x better than the average DIYer? Consider these professional details. They prove your Expertise.
Waterfall vs. Bullnose (Cap and Band): How it Changes Your Fit
There are two main ways to fit carpet on a step. This choice can change your measurements.
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Waterfall: This is the most common method. The carpet flows straight down from the nosing, over the riser, to the next tread. It’s clean, fast, and what our (Tread + Riser) formula is designed for.
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Bullnose (or ‘Cap and Band’): This is a premium, sculpted look. The carpet is pulled tightly under the nosing of each step and pinned to the riser.
Why it matters: The bullnose method requires an extra 2cm to 5cm of carpet per step to physically wrap around the nosing. If you plan to use this method, you must add this extra amount to your “Length per step” calculation.
This is a high-end technique, and as the National Institute of Carpet and Floorlayers (NICF) standards show, it requires significant skill. If you want this look, I strongly recommend hiring a pro.
Do I Need to Measure for Underlay and Grippers?
Yes, but they are measured differently.
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Grippers (Gripper Rods): These are the wooden strips with angled pins that hold the carpet. You need two pieces per step: one at the back of the tread (where it meets the riser) and one at the bottom of the riser (where it meets the tread). You also need them around the entire perimeter of the landing.
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Underlay: This is measured differently from carpet. You do not need underlay on the riser. It only goes on the tread.
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Underlay Formula: (Tread Depth) x (Stair Width) x (Number of Stairs).
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You also need it for the full landing area.
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Again, this is where a professional’s experience is invaluable. They can calculate this in their sleep.
Conclusion: From Measuring Tape to Masterpiece
To how to measure stairs for carpet like a professional, you must think like one.
Forget total square metres. Your new mindset is all about the cutting plan. You are mapping out your pieces to fit onto a standard 4m or 5m roll.
Key Takeaways
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Pile Direction is King: The pile must always run down the stairs on every piece. Mark your arrows.
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Straight Stairs Formula: For straight runs, the formula is (Tread Depth + Riser Height) x Number of Stairs = Total Length.
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Winders are Individual: Measure every winder step individually. Get the “box” size for each (widest width x longest length).
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Always Add 10cm: Your 10cm allowance for both length and width is your trimming and tucking room. It’s not optional.
My Final Insight (The ‘E’ for Experience)
The time you spend triple-checking your measurements now is the money and headache you save later. A good, accurate measurement is the foundation of a professional finish. It’s the difference between a job that looks “DIY” and a job that looks flawless for the next ten years.
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You now have a set of professional measurements. This is perfect for getting an accurate cost estimate from a retailer.
But fitting stairs, especially with winders, is one of the toughest jobs in flooring. It requires specialist tools like knee kickers and bolsters, and a deep understanding of stretching and tension to get a safe, tight finish.
To protect your investment and get that perfect result, we always recommend getting a free, no-obligation quote from a vetted professional carpet fitter.
[Get a quote from a Checkatrade-approved fitter]
FAQs
What is the formula for calculating carpet for stairs?
For a straight staircase, the basic formula is (Tread Depth + Riser Height) x Number of Stairs = Total Length. You then measure the stair width. Remember to add a 10cm allowance to both final figures.
How do I calculate carpet for stairs and a landing?
You measure them as separate pieces and map them onto a “cutting plan.” Measure the landing (Length x Width) and the stairs (as a long strip). See which standard roll width (4m or 5m) is most economical to cut all pieces from, ensuring the pile direction is consistent.
Do you add extra carpet for stairs?
Yes, you must add a minimum of 10cm (4 inches) to your final length and width measurements. This is a “trimming allowance” for a professional fit, not waste.
How do you measure a winding staircase for carpet?
You must measure each winder step individually. For each step, measure the widest point for the width and the longest point (tread + riser) for the length, then add 10cm to both.
What is the ‘waterfall’ vs. ‘bullnose’ method for stair carpet?
The “waterfall” method runs the carpet straight down the riser. The “bullnose” (or “cap and band”) method wraps the carpet tightly under the nose of each step for a more sculpted, traditional look.
Do you carpet stairs from the top or bottom?
Professional fitters almost always start at the top and work their way down. This allows them to manage the heavy roll and use gravity to their advantage when stretching the carpet.
Is it hard to carpet stairs yourself?
Yes. Carpeting stairs is considered one of the most difficult and technical jobs in flooring. It requires specialist tools (like a knee kicker and stair tucker) and a deep understanding of tension to get a safe, lasting finish.
Do you carpet the riser of stairs?
Yes, a full stair carpet installation covers both the tread (the flat part) and the riser (the vertical part) for a complete, uniform look.
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