Stair Square Footage Calculator
Measure stair surface area for carpet, runners, hardwood, or tile installations. Each step has a tread (the part you step on) and a riser (the vertical face).
Stair Area Calculator
Measuring a flight of stairs
For carpet or runners: each step contributes one tread plus one riser. With residential code-typical 11 in tread and 7.5 in riser at 36 in stair width: tread (0.92 × 3) = 2.75 sq ft, riser (0.625 × 3) = 1.88 sq ft, total 4.6 sq ft per step.
A standard 13-step staircase from one floor to the next uses about 60 sq ft of carpet (treads + risers, 36 in width), plus the upper and lower landings.
Carpet, runners, and waste
Wall-to-wall stair carpet wraps the tread and riser. Most installers like to add 6 inches of "wrap" per step for the rounded nosing and tucking. Round up your calculated number by 10% to account for this and matching the pattern across steps.
Stair runners are sold by the linear foot and look better when they're slightly narrower than the stairs (typically 27 or 32 inches on a 36 in stair). Calculate runner length as: (number of steps × tread depth) + (number of steps × riser height) + landing length.
Pro tips
Check for winders and pie steps
Curved or pie-shaped stairs need extra material - the wide outer edge wastes more. Add 20% waste for any stair with winders.
Measure the actual treads, not the plan
Built-out nosing, scribed cuts, and worn treads can vary by 1-2 inches step to step. Measure the actual run width and tread depth, not the architect's number.
Hardwood treads come pre-cut
You can buy stair treads pre-finished in standard sizes (36, 42, 48 in × 11.5 in deep). Count steps, not square feet, when ordering pre-cut treads.
Don't forget bullnose for tile
Tile stair noses need a special bullnose or metal trim piece to wrap the front edge. Order one per step.