Short definition
The two surfaces that make up a stair step — the vertical face (riser) and the horizontal walking surface (tread). Both can take flooring on a carpeted or covered staircase.
A staircase is built from pairs of risers and treads. The tread is the horizontal surface you step on; the riser is the vertical face below the next tread. A standard residential stair in Australia runs about 300 mm tread depth and 180 mm riser height, but the actual figure varies and the takeoff should measure both.
For a carpet stair takeoff, the convention is to measure both surfaces and add them: tread depth plus riser height equals the strip width per step, and the strip runs the full stair width. A 14-step staircase 1 m wide with 300 mm treads and 180 mm risers needs 14 × (0.3 + 0.18) = 6.72 m of stair carpet at 1 m wide, plus a wastage and overlap allowance.
Some installs cover only the tread (an open-riser staircase, or a timber stair with painted risers and a carpet runner on the tread). The takeoff then halves: 14 × 0.3 = 4.2 m at 1 m wide. Always confirm with the customer which surfaces are getting flooring before quoting.
For hard flooring on stairs (vinyl plank, timber boards) the math holds but the install pattern changes — each tread and riser is cut individually rather than wrapped from one continuous strip. The total area is similar; the labour line is higher.
Worked example
14 carpeted stairs, 1 m wide, 300 mm tread + 200 mm riser per step = 14 × 0.5 × 1 = 7 m² of stair carpet, plus the wastage allowance. The flat figure that goes on the quote.