If you want to carpet your stairs, you need accurate measurements before you order anything. To measure stairs for carpet, you count your steps, measure the tread and riser of each one, measure the width, then add extra for seams and waste. Get this wrong and you either run out of carpet halfway up the staircase or pay for material you never use.
This guide from Carpet Land walks you through the entire process step by step, helping you get it right the first time.
Why Accurate Stair Measurements Matter
Stairs are one of the trickiest parts of a home to carpet. Unlike a flat room, every step adds its own tread, riser, and edge that all need to be covered. A small measuring mistake on one step can throw off your entire order.
If you measure short, you may end up with a seam in the wrong spot or a gap that shows bare wood. If you measure long, you waste money on carpet you never use. Getting the numbers right the first time saves you a second trip to the store and keeps your budget on track.
Tools You’ll Need to Measure Stairs for Carpet
You do not need anything fancy to measure stairs for stair carpet. Gather these before you start.
- A steel tape measure, at least 25 feet long
- A pencil and notepad, or a phone with a notes app
- Painter’s tape, to mark spots as you go
- A calculator, for adding up your totals
- A flashlight, if your staircase is dim
A cloth or fabric tape measure can stretch over time, which throws off your numbers. A metal tape measure gives you a more reliable reading.
Understanding Stair Anatomy Before You Measure
Before you start measuring, it helps to know the parts of a staircase. Carpet installers use these words often during carpet installation, and knowing them makes the rest of this guide much easier to follow.
Tread
The tread is the flat part of the step where you place your foot. This is the horizontal surface you measure front to back.
Riser
The riser is the vertical part of the step, between one tread and the next. You measure this from top to bottom.
Nosing
The nosing is the rounded edge of the tread that hangs slightly over the riser below it. Carpet needs to wrap around this edge, so it adds a bit of extra length to each step.
Landing and Winders
A landing is the flat platform where a staircase turns or levels off before continuing. Winders are the pie shaped steps you often see on a staircase that curves instead of turning at a square landing. Both of these need to be measured on their own, separate from the straight steps.
How to Measure Stairs for Carpet Step by Step
Once you know the parts of your staircase, you are ready to start measuring. Work through each step in order and write down every number as you go.
Step 1: Count Your Total Number of Steps
Start at the bottom of the staircase and count every step up to the top. This total tells you how many treads and risers you need to cover, so it is worth doing carefully before you measure anything else.
- Start counting from the very bottom step, not the floor
- Count each winder or pie shaped step on its own
- Write the total down right away so you do not lose count
- Recount once to make sure your number is correct
Step 2: Measure the Tread Depth (Front to Back)
Place your tape measure at the back of the tread, where it meets the riser above, and measure to the front edge. Older staircases are not always perfectly even, so check more than one step before assuming they are all the same.
- Measure the tread depth on at least two or three different steps
- Measure straight across, not on an angle
- Note any steps that come out different from the rest
- Round up slightly if a measurement falls between numbers
Step 3: Measure the Riser Height
Measure from the bottom of one riser to the top, where it meets the tread above. Most home staircases fall between 7 and 8 inches, but you should always check yours rather than assume it matches that range.
- Measure a few different risers, not just the first one
- Keep the tape measure straight up and down
- Write down each measurement as you go
- Flag any riser that looks noticeably taller or shorter
Step 4: Measure the Stair Width
Measure from one side of the staircase to the other, wall to wall or baluster to baluster. Some staircases are slightly wider or narrower at different points, so it helps to check more than one spot.
- Measure the width at the top of the staircase
- Measure the width again at the bottom
- Check the middle if the staircase looks uneven
- Use the smallest width number if they do not all match
Step 5: Account for Nosing
Add a small amount to each tread measurement to cover the nosing, the rounded edge that hangs over the riser below it. This keeps the carpet from pulling too tight over the edge, which can wear through faster over time.
- Add about 1 to 2 inches to each tread measurement
- Check how far your nosing actually extends before adding extra
- Apply this extra amount to every step, not just a few
- Keep this number separate in your notes so it is easy to double check
Step 6: Measure Any Landings or Winders Separately
Measure landings the same way you would measure a small room, in length and width. For winders, measure the narrowest point of each pie-shaped step, especially when planning sisal carpet for stairs, since this is where the carpet gets the most wear.
- Measure landing length and width just like a small room
- Find the narrowest point on each winder step
- Keep landing and winder numbers separate from straight step numbers
- Label each measurement so nothing gets mixed up later
Step 7: Add Extra Length for Seam Allowance and Waste
Once you have your totals, add extra material for pattern matching, seams, and small cutting mistakes. This buffer protects you if a cut does not go perfectly or a pattern needs to line up across steps.
- Add about 10 percent extra to your total length
- Add a bit more if your carpet has a bold pattern to match
- Round up rather than down when your total falls between numbers
- Keep a copy of your final numbers before you order
What Is the 7-11 Rule for Stairs?
The 7-11 rule is a building guideline that says a stair riser should be about 7 inches tall and the tread should be about 11 inches deep. Builders use this rule to keep stairs comfortable and safe to walk on.
This matters for carpet measuring because it gives you a rough idea of what your numbers should look like before you even pull out the tape measure. If your riser or tread measurements come out far outside this range, it is worth double checking your work, since a mistake is more likely than an unusual staircase.
How to Calculate How Much Carpet You Need for Stairs
Once you have your tread, riser, and width numbers, you can figure out your total carpet need.
The Formula: Tread + Riser x Number of Steps
Add your tread depth and your riser height together to get the total length needed for one step. Then multiply that number by how many steps you have. This gives you the total running length of carpet needed, before adding your width and waste allowance.
Example: How Much Carpet for 13 Stairs
Say each tread is 11 inches and each riser is 7 inches. Add those together for 18 inches per step. Multiply 18 inches by 13 steps, which gives you 234 inches, or about 19.5 feet of running length. Add 10 percent for waste, and you land close to 21.5 feet, or roughly 6.5 meters, of carpet length needed for the staircase itself.
How Much Carpet for 12, 14, and 15 Stairs (Quick Reference)
Using the same 18 inch per step estimate, here is a quick reference for other common stair counts. These numbers are estimates only, since your own tread and riser sizes may differ slightly.
| Number of Stairs | Estimated Running Length | With 10% Waste Added |
| 12 stairs | 18 feet | About 20 feet |
| 13 stairs | 19.5 feet | About 21.5 feet |
| 14 stairs | 21 feet | About 23 feet |
| 15 stairs | 22.5 feet | About 25 feet |
Always confirm these numbers against your own measurements before ordering carpet, since even small differences in tread or riser size add up over a full staircase.
How to Measure Carpet for Stairs With a Landing
A landing needs to be measured and calculated separately from the straight run of stairs. Measure the length and width of the landing just like you would a small room, then figure out its square footage on its own.
Once you have that number, add it to your total stair length from the steps above and below the landing. Keep these numbers separate in your notes so your carpet supplier can see exactly how much material goes to the stairs and how much goes to the landing.
Measuring Curved, Winder, or Open Sided Stairs
Not every staircase is a simple straight run, and these variations need a slightly different approach.
Curved and winder stairs have steps that are wider on one side and narrower on the other. Always measure at the narrowest point of each step, since that is where a person’s foot lands most often and where the carpet takes the most wear.
Open sided stairs, which are missing a wall on one or both sides, often need carpet that wraps around the open edge. If your staircase is open on one side, measure a little extra width to account for this wrap, and mention it to your supplier when you order.
Tips for Getting Accurate Stair Measurements
A few small habits make a big difference when measuring stairs.
- Measure every step, not just one or two, since older homes often have small differences from step to step.
- Use a metal tape measure instead of cloth, which can stretch and give you a false reading.
- Write down every number as you go instead of trying to remember them.
- Measure twice before you order, especially on winders and landings.
- Always round up slightly rather than down when you are unsure.
Frequently Asked Questions
Q1. How do you calculate carpet for stairs?
Add your tread depth and riser height together to get the length needed per step, then multiply that by your total number of steps. Add about 10 percent extra for seams and waste to get your final number.
Q2. How do you take measurements for stairs?
Measure the tread depth, riser height, and stair width on each step using a metal tape measure. Measure landings and winders separately, since they are shaped differently than regular steps.
Q3. How much carpet is needed for 12 steps?
Using an average step size of about 18 inches (tread plus riser), 12 steps need roughly 18 feet of running length, or about 20 feet once you add extra for waste. Your exact number depends on your own tread and riser measurements.
Q4. How much carpet do I need for 13 stairs?
Using the same 18 inch average per step, 13 stairs come out to about 19.5 feet of running length, or close to 21.5 feet once you add 10 percent for waste. Check the quick reference table above for other common stair counts.
Q5. How much carpet do I need for 14 or 15 stairs?
A 14 stair staircase needs roughly 21 feet of running length, or about 23 feet with waste added. A 15 stair staircase needs roughly 22.5 feet, or about 25 feet with waste added. These numbers assume a standard 18 inch step size, so always confirm with your own measurements.
Q6. How do you measure winder or curved stairs for carpet?
Measure the narrowest point of each pie shaped step, since that is where the carpet gets the most wear and needs full coverage. Keep these measurements separate from your straight step numbers so your supplier can order the right amount for each section.
Q7. How much carpet do I need for a staircase with a landing?
Measure the landing separately as its own square footage, then add it to the running length of your straight stairs. Keep the two numbers separate so your supplier can order the right amount for each section.
Q8. Is there a free stair carpet calculator?
Yes, several carpet suppliers and home improvement sites offer free online calculators where you enter your tread, riser, width, and number of steps to get an estimate. These tools are a helpful starting point, but a hands on measurement is still the most reliable way to confirm your numbers before ordering.
Conclusion
Measuring stairs for carpet does not have to be complicated. Once you know the parts of a staircase and work through each step carefully, you can get numbers you trust before you spend a dollar on carpet.
Take your time on each measurement, write everything down, and add a bit extra for seams and waste. If your staircase has a landing, a curve, or an open side, do not hesitate to bring in a professional to double check your work. A little extra care now saves you from a costly mistake later.
