SqftKit
SqftKit · Stairs

Stair flooring calculator

Tread area, optional riser faces, waste

A stair flooring calculator treats each tread as its own small rectangle. A staircase is not a room, so length times width of the stairwell overstates or understates the material. Enter how many treads you will cover, how deep and wide each one is, and whether you are also covering the vertical riser faces.

Inputs

Result

Enter the tread count, depth, and width.

Disclaimer: This is an estimate for planning. Measure the real space, read the product label, and confirm anything structural, legal, or financial with a qualified person. Nothing you type is sent to a server. It does not check stair code or structural safety.

A landing is ordinary floor area. Add it on the flooring calculator. Paint for the stair wall is on the ClearQuip paint calculator.

How to use

  1. Count the treads you will cover. A landing is a separate rectangle; add it with the flooring calculator and combine the areas yourself.
  2. Measure one tread’s depth (front to back) and width (side to side) in inches.
  3. If the finish also wraps the vertical face, check the riser box and enter how many faces and how tall they are.
  4. Set a waste percent. Narrow pieces waste more than a big room. Press Calculate.

How it's calculated

One tread (sq ft) = (depth ÷ 12) × (width ÷ 12)
Tread area = one tread × number of treads
Riser area = (riser height ÷ 12) × (width ÷ 12) × riser count
Order = (tread area + riser area) × (1 + waste ÷ 100)

Dividing by 12 converts inches to feet before multiplying, so the product is square feet. Risers are optional and use the same width as the tread, which is right when the riser is the same width as the step and wrong when the skirt board covers the ends. Adjust the width if the finished face is narrower.

This is not a stair-builder. Rise, run, and headroom rules are local code, and this page never claims a stair is legal. It only totals the surface you said you will cover. Carpet in square yards for a whole flight is easier if you already know the square feet and divide by 9 on the carpet calculator.

Worked example

Thirteen treads, each 10 inches deep and 36 inches wide: one tread is (10 ÷ 12) × (36 ÷ 12) = 2.5 square feet. Thirteen treads are 32.5 square feet. Twelve risers at 7.5 inches tall add (7.5 ÷ 12) × (36 ÷ 12) × 12 = 22.5 square feet. The combined 55 square feet, plus 10 percent waste, orders 60.5 square feet.

Assumptions and sources

The arithmetic is rectangle area with an inch-to-foot conversion of 12. The example’s 10 inch depth and 7.5 inch riser are sample measurements, not a code requirement. Nosing that sticks past the riser is extra depth; include it in the tread depth if you will cover it. Waste is a percent you choose because cutoffs on stair noses are hard to reuse.

FAQ

How many treads does a stair have?

One fewer tread than the number of risers is common when the top step lands on the upper floor, but existing stairs vary. Count the surfaces you will actually cover.

Should the landing go in this form?

No. A landing is a floor rectangle. Calculate it separately and add the square feet to the stair total.

What waste percent is reasonable on stairs?

Stairs produce more offcuts than a rectangular room. Ten percent is only the default in the form. Raise it if every piece is a short nosing.

Does this tell me if the stair meets code?

No. It does not check riser height, tread depth, or handrails. Those rules come from your local building code.

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