Measuring a staircase for carpet
Carpet estimating on stairs isn't a floor-area problem — it's a linear-footage problem. Get the per-step numbers right and the yardage takes care of itself.
Count the steps
Count every riser in the flight, top to bottom. If you already ran the Stair Rise and Run Calculator for this staircase, use the same step count here — it's the number that drives everything else on this page.
Measure tread depth and riser height
Measure the tread from the face of the riser below to the nosing edge — not just the flat walking surface, since carpet has to wrap the overhang too. Measure riser height from tread surface to tread surface, not to the top of the nosing.
Measure stair width
Measure wall-to-wall on a closed stair, or rail-post-to-rail-post on an open one. This is the width of every strip cut from the roll, so get it at a few points — treads aren't always perfectly square to the wall.
Pick your install method
Waterfall and captured need the full riser-plus-tread wrap. Hollywood, used on open-riser stairs where the riser stays exposed, only carpets the tread — pick it and the calculator drops the riser length automatically.
The four formulas behind every result
Nothing on this page is a black box. Here's exactly what runs when you change a number.
Per-Step Length
Ease covers the nosing wrap and corner tuck: roughly 2" for waterfall, 3" for captured. Hollywood drops the riser term entirely since the riser stays bare.
Total Stair Run
Per-step length times step count, plus one pattern-repeat length if you're matching a patterned carpet, so the repeat can start clean at the top of the flight.
Coverage to Yardage
Run and width in inches gives square inches; divide by 144 for square feet, then by 9 for square yards — the unit carpet is actually sold in.
Order Quantity
Apply the waste factor, then round up to the next whole yard — stair-carpet cuts are billed by the yard, and a fractional yard still costs a full one.
Walking through a real 14-step flight
Same stair as the Stair Rise and Run Calculator's 108" worked example — 14 steps, a 7.71" actual riser, a 10" tread (floored at the IRC minimum), 36" wide, waterfall style, no landing, no pattern, cut from a 12' roll.
Per-step length
Waterfall ease is 2": 10" tread + 7.71" riser + 2" ease = 19.71" per step. That's the length of carpet consumed for every single riser you climb.
Total stair run
19.71" × 14 steps = 275.94" (about 23'0"). No landing and no pattern repeat in this example, so nothing else gets added to the run.
Coverage in square yards
275.94" run × 36" width = 9,933.8 sq in ÷ 144 = 68.99 sq ft ÷ 9 = 7.67 sq yd of raw coverage, before any waste is added.
Order quantity
Waterfall's auto waste factor is 10%: 68.99 sq ft × 1.10 = 75.89 sq ft = 8.43 sq yd, which rounds up to 9 sq yd to order — the number a retailer will actually cut and bill. This is a direct example of why the order quantity almost always looks bigger than the "coverage" number a homeowner calculates by hand: waste and whole-yard rounding both push it up, and skipping either step is the single most common reason a stair carpet order comes up short mid-installation.
Install methods compared
The same stair takes noticeably different amounts of carpet, and noticeably different labor, depending on which of these three methods you pick.
| Method | Per-Step Allowance | Typical Waste | Look & Labor |
|---|---|---|---|
| Waterfall | Tread + Riser + 2" | 8–10% | Carpet drapes over the nosing and falls straight to the next tread without being shaped into the inside corner. Fastest install, the most common builder-grade method. |
| Captured (cap-and-band) | Tread + Riser + 3" | 12–15% | Carpet is tucked and shaped into every riser-to-tread corner for a fully upholstered look. Most labor-intensive, needs an experienced installer. |
| Hollywood (open riser) | Tread + 2" (no riser) | 8–10% | Only the tread is carpeted; the riser stays exposed wood, paint, or is open entirely. Only works on a stair actually built with open or finished risers. |
Comparing carpet against a hard-surface finish on the same stair? Use the Carpet vs Hardwood Stair Cost Calculator.
Standard broadloom carpet roll widths
Roll width rarely limits a single stair flight — most stairs are 30"–48" wide, well under any of these. It matters more when a job cuts multiple strips from the same roll.
| Roll Width | Inches | Best For | 36" Stair: Strips per Width |
|---|---|---|---|
| 12 ft | 144" | Most common, widest style selection | 4 |
| 13'6" | 162" | Slightly wider rooms, fewer seams | 4 |
| 15 ft | 180" | Large open areas, "wide goods" | 5 |
Reference only — confirm available widths with your specific carpet style, since not every color runs in every width.
Padding, tack strip & pattern matching
A stair carpet order that's perfectly sized in square yards can still come up short on the job if these three items get skipped.
Padding is a separate order
Padding covers roughly the same area as the carpet but is bought and billed separately, usually with a smaller 5% waste allowance since it isn't pattern-matched. Stair-rated pad is denser than flat-floor pad — a too-soft pad on a stair feels spongy underfoot and wears the carpet backing faster at the nosing.
Tack strip at every break
Gripper strip is typically nailed at the base of every riser and the back of every tread to hold the carpet in the step profile — not just at the top and bottom of the flight. Hollywood only needs one strip per tread since there's no riser to anchor. [VERIFY: confirm the two-strips-per-step convention against your local installer's standard practice — placement varies by pad thickness and carpet backing.]
Pattern repeat compounds fast
A patterned or striped carpet has to realign at the start of the flight and again at any landing seam. This calculator adds one repeat length as a simplification; a large repeat (24"+) on a long flight can justify a bigger allowance — ask your installer to confirm before ordering.
Nosing overhang isn't free
If the tread overhangs the riser below by an inch or more, that overhang still has to be wrapped in carpet. Measure tread depth to the true face of the riser, including the overhang, not just the flat part underfoot.
These are estimating-stage figures, not an installer's cut list. A tight winder stair, a curved flight, or an unusual nosing profile should get a template or an in-person measure before ordering.
Common mistakes when ordering stair carpet
Most stair carpet shortages trace back to one of these five estimating errors, not to bad installation.
Measuring the tread only
Forgetting the riser wrap is the single most common under-order on stairs — it can leave the estimate short by nearly half the actual yardage needed.
Ignoring the nosing overhang
Tread depth measured to the flat walking surface, not the true overhanging edge, quietly shorts every single step by the overhang amount.
Skipping the pattern repeat allowance
A striped or patterned carpet with no repeat allowance in the order runs short mid-install, once the pattern has to be re-aligned at a seam or landing.
Assuming padding is included
Padding is a separate line item with its own waste factor and its own pricing — it's easy to budget carpet alone and get surprised by the pad invoice.
Ordering to the exact calculated yardage
Rounding down to save a few dollars on the last fractional yard is the fastest way to be one step short of carpet on install day, with no matching dye lot available to finish the job.
When to use a stair carpet calculator
Stair carpet yardage comes up any time a flight is getting a new soft-surface finish, whether that's a full remodel or a quick refresh.
Whole-House Remodel
Bidding stair carpet as one line item alongside room-by-room flooring quotes.
Replacing Worn Stair Carpet
Re-carpeting a flight without touching the rest of the house's flooring.
Basement Stair Finishing
Sizing carpet for a newly framed basement stair before move-in.
New Construction Estimating
Getting a material number into the budget before the flooring subcontractor bids it.
Rental Turnover
Quick yardage check before ordering builder-grade carpet between tenants.
DIY Budget Check
Sanity-checking a retailer's quoted yardage before signing off on the order.