How to measure stairs for carpet.

1. Learn the parts of a staircase.

• Tread: the flat part you step on.
• Riser: the vertical face between two treads.
• Nosing: the front edge of the tread, which often sticks out past the riser below.
• Landing: a flat platform where the stairs pause or turn.
• Pie or winder steps: wedge-shaped steps that turn a corner. Each one can be a different size.
• Starter or bullnose step: a wider bottom step, often with one or two rounded ends.
• Open or floating steps: steps with no riser or with an exposed side. Carpet may need to wrap the edges, and some open designs do not suit carpet at all. Ask the installer.

Count treads and risers separately. A straight flight often has one more riser than treads, because the top riser meets the upper floor.

2. Take three measurements for each step.

For each step, record the width, the tread depth and the riser height. Inches work best for stairs: the numbers are small and you avoid decimal mistakes.

• Width: measure across the tread from wall to wall, or to the outside edge on an open side. Measure at the front and the back, because walls are not always parallel. Use the wider reading.
• Tread depth: measure from the back of the tread, where it meets the riser above, to the front of the nosing.
• Riser height: measure the vertical face from the tread surface up to the underside of the nosing above.

Write down where each number starts and ends. An installer reading “10 in tread” needs to know whether the nosing is included.

3. Measure each group of matching steps.

In a straight flight, most steps are the same size. Measure three or four of them. If they match, record one size and the number of steps. If one is different, list it on its own.

Pie steps need individual measurements. Measure the width along the outside edge, where the step is widest, and the depth at its deepest point. A starter step is wider and deeper than the rest. Measure its full width including the rounded ends, because a bullnose takes extra carpet to wrap. For open or floating steps, note which sides are exposed.

A simple stair list might read: 12 straight steps at 36 × 10 × 7.5 in, 3 pie steps measured one by one, 1 starter step and 1 landing.

4. Measure each landing like a small floor.

Measure a landing’s length and width and multiply them, just like a room. An L-shaped landing splits into two rectangles. Note the front edge where the landing drops to the next step, because that edge usually gets a nosing wrap too. Measure each landing separately, even if two look the same.

5. Work out the carpet area for a straight flight.

Each step needs carpet across its width and from the back of the tread down the riser. Add the tread depth and the riser height to get the carpet length per step, then multiply by the width.

If the flight has a 14th riser at the top, add 36 × 7.5 = 270 sq in, or 1.88 sq ft. Add each landing separately: the 36 in × 40 in landing above brings the steps and landing to 56.88 + 10 = 66.88 sq ft. These figures are measured surface area only, before nosing wrap, cutting and waste. They are not an order quantity.

6. Let the installer decide the nosing wrap and the cuts.

How the carpet wraps the nosing changes how much is used. A waterfall style flows over the nosing and straight down to the next tread. A wrapped style, sometimes called upholstered or Hollywood, is pulled tight around the nosing and fastened underneath. Each method uses a different amount of carpet per step, and the installer chooses based on the carpet and the stairs.

Stair pieces are cut from a roll of fixed width. The installer works out how many step pieces fit across the roll, which way the pile must run and how to match a pattern from step to step. Pie steps and bullnose ends leave offcuts. That is why the measured area is a starting point for the conversation, not the amount to buy. The Carpet and Rug Institute’s installation standards include guidance on installing carpet on stairs.

Measure stairs with I Measure Pro.

I Measure Pro has a stairs mode. Pick the step types in your staircase: rectangular, pie, starter, floating and landing. Then measure one width, depth and riser height for each size group with the phone camera, or type the sizes in. Each landing is measured separately. The staircase is saved as its own area in the project, alongside the rooms.

Stair drawings are schematics, so rely on the numbers rather than the picture. Confirm sizes with a tape before ordering or cutting, and give the installer your step list, not a finished cut plan. See how to measure a room for carpet for the rooms on the same job, and check supported Android phones before you download.