Stair Square Footage Calculator

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.

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.

Stairs are measured by tread × riser × number of steps, not by overall stair footprint. Each tread (the horizontal surface you step on) plus riser (the vertical face) creates the unit of square footage per step.

Standard residential stair dimensions: 36 inches wide × 11 inches tread depth × 7 inches riser height. Including the 1.5-inch nosing wrap, one step provides 30 × 19.5 = 585 sq in = 4.06 sq ft of material surface (for carpet, runner, or laminate).

Worked example: a typical 13-step staircase between floors. 13 × 4.06 = 52.8 sq ft of material needed. Add 15-20% waste for cuts and pile direction = 60-65 sq ft.

Stair width varies more than you'd think: code minimum is 36 inches; standard residential is 36-44 inches; grand staircases can be 48-60 inches. Each additional inch of width adds proportional sq ft.

Each stair material has different square footage requirements because of how the material wraps the step:

Carpet: covers the entire tread + riser + nosing in one piece. 4.06 sq ft per step. Standard waste 20% because of pile direction.

Carpet runner (centered, exposed wood on sides): typically 27-32 inches wide, so reduce step coverage proportionally. 32-inch runner on 36-inch step = 28 inches usable × 19.5 inches = 3.79 sq ft per step.

Hardwood treads + risers as separate pieces: a tread is typically 1.25 × 11.5 × 36 inches (plus 1.25-inch overhang to the riser below). Each step uses 1 tread piece and 1 riser piece (7 × 36 inches). The tread material is sold as 'stair tread' lumber, more expensive than regular hardwood per board foot.

Laminate or LVP on stairs: requires special bullnose pieces. Most plank flooring isn't designed for stairs — needs separate tread/riser/nosing components, sold as a 'stair kit' per step. 13-step staircase needs 13 tread kits.

Stair projects include more than just the steps. A full stair refinish includes:

Steps: 4-6 sq ft per step depending on width.

Risers (vertical face under each tread): 7 × 36 = 252 sq in = 1.75 sq ft per step if separately finished. Often painted instead of covered.

Top landing and bottom landing: usually 36 × 48 inches = 12 sq ft each.

Nosing wrap: the rounded edge where tread meets riser. Carpet wraps this naturally; hardwood and laminate need a separate bullnose component.

Stair railings, balusters, newel posts: these don't add to square footage but typically add $300-1,500 per stair run to a refinish project.

Total project cost: $1,000-4,000 for carpet on a 13-step run. $2,500-8,000 for hardwood treads and risers. $3,000-10,000+ for full refinish with handrail and balusters.