Stair Carpet Runner Calculator

How much carpet does a staircase need?

Ordering stair carpet is a job where a small measuring error becomes a visible problem, because a runner that comes up short cannot be stretched, and a join in the middle of a flight is both ugly and a weak point under daily foot traffic. The calculation itself is straightforward: each step consumes one tread depth plus one riser height of carpet, as the runner folds over the nosing and down the riser, and the total is that sum multiplied by the number of steps. The calculator on this page does exactly that, converting centimetres to metres, so a standard flight of thirteen steps with twenty-five-centimetre treads and eighteen-centimetre risers needs five point five nine metres of runner.

That figure is the net length, and a sensible order adds a little more. Allow extra at the top and bottom of the flight for finishing: the runner usually continues a short way onto the landing at the top and finishes neatly at the bottom step, and a professional fitter will want a margin for trimming and for the waterfall or cap-and-band fitting method chosen. A good rule is to add about half a metre for a straight flight, and more for flights with winders or a landing, where the runner must be cut and matched around turns. Winders, the triangular steps on a turning stair, consume more carpet than straight steps, because each winder is effectively wider on one side, so measure winders individually rather than treating them as standard steps.

Measuring treads and risers correctly

Measure tread depth from the face of one riser to the face of the next, or, more practically, from the nosing edge to the back of the tread, and measure riser height from the top of one tread to the top of the next. Measure several steps and use the largest figures, because stairs are rarely perfectly uniform, especially in older houses, and the carpet must fit the biggest step, not the average. Count every step, including the bottom step from the floor and the top step onto the landing, and note whether the top and bottom are full steps or landings, because landings are carpeted separately and need their own area calculation. If the staircase has a landing halfway, treat it as two flights plus the landing area.

Runner width and fitting methods

Runners are usually narrower than the staircase, leaving painted or wooden stair edges visible on both sides, and the classic look leaves about ten to fifteen centimetres of bare stair on each side. For a staircase ninety centimetres wide, a sixty to seventy-centimetre runner looks balanced; for a wider stair, seventy to eighty centimetres works well. Full-width stair carpet, fitted wall to wall, is measured differently, by area rather than runner length, and needs about the same length but the full width, plus extra for cutting around spindles and newel posts. If your stair has a banister with spindles on one side, fitting takes longer and wastes more carpet, so mention it when ordering or quoting.

There are two main fitting methods, and they affect how the carpet behaves. The waterfall method lets the carpet fall straight from tread nosing to the next tread, leaving a small gap behind the nosing, which is faster and uses slightly less carpet. The cap-and-band method folds the carpet tightly around each nosing and down the riser, giving a tailored look that shows the stair profile, but it uses a little more carpet and takes longer to fit. The calculator's length works for both, because the difference is a few centimetres per step at most, well within the finishing allowance. Whichever method you choose, underlay matters: a good stair underlay adds comfort, reduces wear, and helps the carpet grip, and it is measured at the same length as the runner.

Choosing stair carpet that lasts

Stairs are the hardest-wearing carpeted surface in a house, because every footfall lands on the same narrow nosing edge, so durability matters more than softness. Wool and wool-blend carpets wear beautifully and resist crushing, while high-quality nylon offers excellent stain resistance and value. Avoid very deep pile on stairs, because it wears unevenly at the nosing and can be a trip hazard, and avoid loop pile that can snag on shoes or pet claws. A medium pile with a dense construction, in a colour that hides the traffic path, will look good far longer than a pale plush carpet that shows every footprint. Patterned carpets hide wear best of all, but patterns must be matched across steps, which increases waste and fitting skill required.

Colour and pattern deserve a moment of thought, because stairs are highly visible and hard to change. Mid-tones and subtle patterns hide dust and wear between cleanings, while very light colours show the traffic path within months and very dark colours show lint and pet hair. If you are matching existing landing carpet, order all of it together from the same dye lot, because a runner fitted months later may differ in shade. Keep an offcut after fitting: it is invaluable for a future repair, for matching if you extend the carpet, and for testing cleaning products before using them on the stairs themselves.

Installation tips and safety

Professional fitting is worth the cost for stairs, because a poorly fitted runner wrinkles, shifts, and wears out quickly, and the tools and techniques, including a knee kicker and stair tool, are not part of a typical DIY kit. If you do fit it yourself, fix gripper rods on every tread and riser, stretch the carpet firmly at each step, and trim carefully at the nosing, because a loose runner is a trip hazard. Keep the runner centred, with equal margins on both sides, and check alignment from the bottom of the flight, where the eye notices crookedness first. Stair rods, the decorative bars across each tread, are optional and purely decorative on a fitted runner, but they can finish the look in a traditional hallway.

• Count every step, including bottom and top steps.
• Measure several steps and use the largest tread and riser.
• Add about 0.5 m for finishing at top and bottom.
• Measure winders and landings separately.
• Choose dense, medium-pile carpet for stair durability.

A well-measured runner arrives as one continuous piece, fits without a join, and transforms a staircase. Use the calculator above to get your length, add the finishing allowance, and order with confidence.

Keeping stair carpet looking good

Stair carpet earns its wear honestly, but a little maintenance extends its life noticeably. Vacuum stairs weekly with a crevice tool, working from top to bottom and paying attention to the nosing edge, where grit collects and grinds into fibres underfoot. Treat spills immediately, blotting rather than rubbing, because rubbing spreads a stain and damages pile. Deep-clean stairs every six to twelve months, depending on traffic, with a method suited to the fibre, and test any cleaning product on your saved offcut first. Rotate a runner if the design allows, though most fitted runners cannot be rotated, so instead protect the most-worn steps with a clear stair tread cover if the household includes pets or heavy boots. Replace underlay when it flattens, because worn underlay accelerates carpet wear far more than most people realise.