3ft Stair Runner: Sizing, Reveal Maths and Buying Guide

What stair width suits a 36in runner

A 36in runner is sized to leave a visible border of bare tread — the 'reveal' — on each side once it is centred and fixed. The comfortable range for that reveal is roughly 2-4.5in (5-11cm) each side; narrower than that and the runner looks jammed against the strings, wider than that and it starts to look lost in the middle of the tread. Working back from that reveal range, a 36in runner suits a staircase that measures 39-44in (99-112cm) stair width between the strings (or between the wall and the baluster on an open side).

Exact reveal maths for your stair

The formula is simple: (stair width − runner width) ÷ 2 = reveal on each side, assuming the runner is centred, which it should be on almost every straight flight. For a 36in runner on a stair measuring, say, 42in between the strings, that's (42 − 36) ÷ 2 = 2.8in of bare tread down each side. Measure the clear width at three points — top, middle and bottom of the flight — because most staircases taper by a few millimetres over their length, and the reveal should be calculated from the narrowest point so the runner never overhangs the tread nosing anywhere.

Roll widths and metric equivalents

Stair runners are cut from broadloom carpet, so the width you buy is set by the loom width the mill weaves, not by an arbitrary inch measurement. A 36in runner is almost always cut from 91cm (36in) — full broadloom width, the practical ceiling for an off-the-shelf runner before bespoke run-length weaving. When comparing products between UK, US and European suppliers, always check the centimetre figure — an 'inch' size is often a rounded label over a genuine metric width, and a difference of a centimetre either way changes your reveal by 5mm each side.

'3ft' as a search term vs the inch size

A '3ft stair runner' and a '36in stair runner' are the same product — 3 feet is exactly 36in (91cm). People search in feet when they've measured their stair with a tape that reads in feet and inches and want a round number to shop against, but every supplier lists stock by the inch or centimetre figure, not by the foot. Convert your foot measurement to inches before you search or order, and treat any listing that only says '3ft' with suspicion — confirm the exact inch or cm width before buying, because roll widths cluster around a few standard sizes and a supplier's '3ft' might round to a slightly different one.

Rod and holder width for this runner

Stair rods and holder bars need to clear the runner by roughly 25-40mm (1-1.6in) in total — about the same overhang on each end, excluding any finials. For a 36in runner that means a rod length (before finials) of roughly 37-37.6in (94-96cm). Confirm this against your actual stair width too — the rod must sit clear of the strings, not just clear of the runner, so on a stair near the top of this runner's range the rod length is set by the string gap rather than by the runner edge. Work out exact holder counts and lengths with the stair runner rods calculator.

Where this width looks wrong

• On a stair narrower than about 36in (91cm): the reveal disappears and the runner reads as wall-to-wall carpet rather than a runner.
• On a stair wider than about 48in (122cm): the runner looks like a narrow strip lost in the middle of a wide tread — step up a size.
• On a staircase with a strong taper: a reveal that is correct at the top and negative at the bottom, so the runner appears to run off the tread.
• Where the newel posts are wide and boxy: a narrow runner beside a chunky post looks under-scaled; measure the reveal against the post, not just the string.
• On winders and curved sections: this straight-flight sizing does not apply — winders need bespoke width planning, usually handled with a template.

Worked yardage example: 13-step flight

Take a flight of 13 steps with a 11in tread depth and a 8in riser height, plus a 5in return onto the landing at the top. The 'going' of carpet needed per step is tread plus riser: 11 + 8 = 19in. Across 13 steps that's 19 × 13 = 247.0in, plus the 5in landing allowance, giving a total run of 252.0in (21.00ft, 6.40m).

36in vs the next size up or down

Fitting and stock notes for this width

Because both 2ft and 3ft sizes describe standard broadloom widths, they're usually held in stock rather than made to order, so lead times are typically shorter than for the in-between or metric sizes. It's still worth double-checking the exact cm figure a supplier quotes against 61cm or 91cm — a listing that's out by even a centimetre changes your reveal calculation, and foot-based searches are the most common place for that kind of rounding to slip through unnoticed.

Buying checklist for this width

1. Measure your stair's clear width at top, middle and bottom; use the narrowest figure.
2. Confirm 36in gives a reveal in the 2-4.5in range at that narrowest point.
3. Check the supplier's exact cm figure against the 91cm standard for this size, not just the inch label.
4. Calculate total run length (tread + riser × steps + landing) and add 10% for waste.
5. Round the order up to a full yard or metre and confirm dye-lot consistency for the full length.
6. Size rods or holders to roughly 37-37.6in, excluding finials, and clear of the strings.

Whatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.