How to measure for a stair runner

Why measuring stairs is different from measuring a room

Measuring flat flooring is a matter of area: length times width, with an allowance for wastage at the edges. A staircase is not flat, and it is not one surface — it is a repeating sequence of horizontal and vertical faces joined at a nosing that consumes material every time the runner turns the corner. Two staircases with an identical vertical rise can need noticeably different lengths of runner if their tread depth, riser height or nosing profile differ. That is why a generic "length per step" rule of thumb is only a starting point, and why the formula below asks for your own measurements rather than an average figure.

The stair runner length formula

Written out, the calculation is:

Total length = ((tread depth + riser height + nosing allowance) × number of risers) + landing runs + waste allowance

The nosing allowance covers the fabric consumed as the runner curves over the projecting front edge of each tread. A shallow, square-edged tread uses less; a deep bullnose profile uses more. Measure the projection of your nosing and use that figure rather than a guess where the profile is pronounced.

Worked example

A straight flight of 13 risers, 10 in treads, 7.5 in risers, 1.25 in nosing wrap:

• Per step: 10 + 7.5 + 1.25 = 18.75 in
• Stair run: 18.75 × 13 = 243.75 in (20.3 ft)
• Waste at 10%: 24.4 in
• Order length: 268.2 in — about 22.4 ft, or 7.5 yd

Runner sold by the running foot is usually quoted in feet, so round up to the next whole foot. Woven runners sold by the yard round up to the next yard.

A second worked example, with a landing

A dog-leg staircase with two flights of 8 risers each, joined by a 40 in landing, treads 10.5 in and risers 7 in, nosing wrap 1 in:

• Per step: 10.5 + 7 + 1 = 18.5 in
• Both flights: 18.5 × 16 = 296 in
• Plus landing run: 296 + 40 = 336 in
• Waste at 12% (turn adds complexity): 40.3 in
• Order length: 376.3 in — about 31.4 ft, or roughly 10.5 yd

Notice the waste allowance moved up slightly from the first example. That is a judgement call, not a fixed rule — turns, joins and pattern-matching all justify a higher allowance than a plain straight flight.

How to take the measurements accurately

1. Count the risers. Every step contributes one tread and one riser. The top riser finishes at the landing, so the riser count is the number to multiply by.
2. Measure a typical mid-flight step, not the bottom one. Bottom steps are frequently deeper or bullnosed.
3. Spot-check three steps. If tread depth varies by more than about ¼ in (6 mm), measure every step and total them individually.
4. Measure the nosing projection from the face of the riser to the front edge of the tread above.
5. Measure stair width at the narrowest point, usually where a skirting board or stringer intrudes.
6. Record every figure in a simple table as you go — step number, tread depth, riser height, and any note about irregularity. This turns a fifteen-minute job into a document you or a fitter can check later without climbing the stairs again.

Choosing the width

Runner width is a proportion decision, not a fixed rule. The margin of visible tread on each side should look deliberate and stay even up the flight.

Narrow margins of under 2 in (5 cm) tend to read as a fitting error rather than a design choice, and they are awkward to clean. Very wide margins leave more timber exposed to wear. On a staircase that varies in width, set the runner to the narrowest step and centre it consistently; a runner that follows the wall will drift visibly. The full reasoning behind margin choice, including how it interacts with stringer style, is set out in the stair runner width guide.

Special cases

Landings

Measure a landing as a flat run and add it to the total. Where the runner turns across a landing, an experienced fitter will usually cut and re-join the material so the pile direction and pattern continue correctly rather than folding it round the corner. See how a runner is finished at the top of the stairs for the detail of that junction.

Winder stairs

Winders are wedge-shaped, so each one is measured on its own. Take the depth along the longest edge of the tread — the outside of the turn — because that is the line the runner must cover. Winders consume material quickly and are the main reason a real quote exceeds a straight-flight estimate. They are also the strongest argument for professional measurement and fitting. The winder stair runner guide covers how the material is shaped and joined around the turn.

Bullnose or curved bottom steps

A bullnose step is wider and rounded, so it needs its own measurement and often a separate piece of material shaped to the curve. Measure across the widest point of the curve, not the straight width above.

Patterned material

A pattern that must land in the same place on every tread needs extra material equal to roughly one pattern repeat per join. Ask the supplier for the repeat length before you order and add it to the waste allowance. Stripes and directional patterns also need a consistent pile direction, so the whole run should come from a single roll or dye lot.

Open-sided and narrow staircases

On an open-sided staircase, the runner's edge on the open side has no stringer to define it, so the margin has to be judged against the baluster line rather than a fixed board. Measure to the inside face of the balusters and keep a slightly wider margin than you would on an enclosed side, since an edge that overhangs an open side is both visually awkward and a genuine trip risk.

Common measurement mistakes

• Counting treads instead of risers, which loses a step of material.
• Measuring the bottom step and applying it to the whole flight.
• Ignoring the nosing wrap, which quietly shortens the runner by a foot or more.
• Ordering to the exact calculated length with no waste allowance.
• Setting width from the widest step, so the margins pinch further up.
• Forgetting to measure the landing separately, so the total quietly falls short by the landing's length.
• Measuring in a hurry with the tape held at an angle, which inflates every reading slightly and compounds over a long flight.

What to do with the finished measurements

Once you have a length and width you trust, use them consistently through the rest of the project. Quote the same figures to every supplier so comparisons are like for like, and keep the original notes — tread depth, riser height, nosing projection, width at the narrowest point — because a fitter will want to verify them on site rather than take a total figure on trust. If the numbers feed into a cost estimate, small rounding decisions here (whole feet versus exact inches) can move the total more than people expect on long flights.

Measuring for a bullnose bottom step

A bullnose or curtail step is the rounded, wider step at the very base of many traditional staircases. Measuring it requires a different approach to the standard rectangular tread. Because the runner must curve around the outer edge of the bullnose, you cannot simply use a straight width measurement. Instead, use a flexible tape measure to follow the outer perimeter of the curve where the runner will sit. If you are fitting a separate piece of carpet to the bullnose, record the maximum depth and the total arc length. This is one of the most common areas for measurement errors, so recording the step as a "feature step" with its own specific dimensions is essential for a clean professional finish.

Calculating for stair runners on winders

Winder stairs are wedge-shaped steps used to turn a corner without a landing. Because they are narrow at one end and wide at the other, measuring them requires finding the "walking line" — typically the path taken about 30cm (12 inches) from the narrow end. However, for material estimation, you must measure the deepest part of the tread (the outer edge). A common professional technique is to measure the widest diagonal of the winder and add that to the total run. Winders consume material significantly faster than straight flights, and the waste allowance should be increased to at least 15-20% if the flight contains multiple turns, as pattern matching on curved sections requires more flexibility in where cuts are made.

Handling pattern repeats and wastage

When ordering a patterned runner, the "waste allowance" is not just for mistakes; it is for geometry. If a runner has a 30cm (12 inch) pattern repeat, and your step length (tread + riser + wrap) is 45cm (18 inches), the pattern will naturally shift on every step. To ensure the pattern lands in the exact same spot on every tread for a symmetric look, the fitter may need to trim and join the runner at the crease of every step. This "cut and shut" method consumes much more material than a continuous run. Always check the pattern repeat dimension on the manufacturer specification and, if in doubt, order an extra 20% to avoid being left short at the top of the flight where dye-lot differences would be most visible.