Quick Answer
To measure stairs for carpet, measure the tread depth and riser height of each step, add them together for the run per step, then multiply by the number of steps and the stair width. Add a 10 to 15 percent waste allowance for cutting and fitting, more if the carpet has a pattern. Measure landings separately and add them to your total before ordering.
What You’ll Need
- A tape measure, ideally a metal one for accuracy on hard edges
- A notepad or worksheet to record each step’s measurements individually
- A pencil to sketch a rough layout of the staircase, noting any turns or landings
Step-by-Step Measuring Method
- Measure the tread depth, the horizontal part you step on, from front to back for each step
- Measure the riser height, the vertical part between each step, for the same step
- Add tread depth and riser height together to get the run per step
- Repeat for every step individually, since older or uneven staircases can vary slightly step to step
- Measure the stair width from side to side at its widest point
- Multiply the total combined run by the stair width to calculate the base carpet area
- Measure any landings separately, treating each as its own rectangle, and add this area to your total
Worked Example
For a straight staircase with 12 steps, each with a tread depth of 25cm and riser height of 18cm, the run per step is 43cm. Multiplied across 12 steps, that gives a total run of 516cm. At a stair width of 90cm, the base area works out to roughly 4.64 square metres, before adding landing carpet and a waste allowance on top.
Adding Your Waste Allowance
| Carpet Type | Recommended Waste Allowance |
|---|---|
| Plain, straight staircase | 10 percent |
| Staircase with turns or winders | 15 to 20 percent |
| Patterned carpet, any staircase shape | 20 to 25 percent for pattern matching |
Common Measuring Mistakes
- Measuring only one step and assuming every step is identical, when older properties often have slightly uneven treads and risers
- Forgetting to include the nosing wrap, the extra fabric that tucks under the front edge of each step, typically an additional 30 to 50mm per step
- Not measuring landings separately, leading to a shortfall when the carpet arrives
- Underestimating waste allowance on patterned carpet, where pattern alignment can use significantly more material than expected
- Not accounting for winder or curved sections, which need individual templates and use noticeably more carpet per step than straight flights
Ordering Extra for Waste
Once you have your total base area including landings, add your chosen waste percentage on top before converting to the units your supplier sells in, typically square metres or linear metres depending on roll width. It is generally far better to order slightly too much than too little, since carpet dye lots can vary between production runs, making it difficult to get an exact colour match if you need to order more later.
Related Reading
Once you know how much carpet you need, see our guide on how much carpet costs to budget the full project.
Frequently Asked Questions
Do I need to measure every step individually?
Yes, particularly in older properties, since tread depth and riser height can vary slightly from step to step even on the same staircase.
How much extra carpet should I order for stairs?
Around 10 to 15 percent for a straight staircase, rising to 20 to 25 percent for patterned carpet or staircases with turns and winders.
Do landings need separate measurements?
Yes, measure each landing as its own rectangle and add the area to your total stair carpet calculation.
What is nosing wrap and why does it matter?
It is the extra carpet that wraps under the front edge of each step, typically 30 to 50mm, and needs to be included or your carpet will fall short at each stair edge.
Do spiral or winder staircases need a different measuring approach?
Yes, each tread is often a unique shape, so individual templates and a higher waste allowance are typically needed compared with a straight flight.