How Many Stairs for 8, 9, 10 or 12 Feet?

The number of stairs depends on the floor-to-floor height and the tallest riser you accept. Here are common heights worked out, with the run each one needs and where a landing becomes necessary.

Published 2026-10-24 by Blissom Apps · Every row is computed by the site's tested stair engine

Floor-to-floor heights in feet

Two versions of each height: risers up to 7 3/4 in (the IRC maximum for houses) with 10 1/2 in goings, and a gentler stair with risers up to 7 in and 11 in goings (the "7-11" stair). Treads are risers − 1, because the upper floor is the top step.

Risers, treads and run by floor-to-floor height
Rise	Risers (≤ 7 3/4 in)	Riser height	Treads	Run at 10 1/2 in	Risers (≤ 7 in)	Run at 11 in	Note
7 ft	11	7 5/8 in	10	8 ft 9 in	12	10 ft 1 in
8 ft	13	7 3/8 in	12	10 ft 6 in	14	11 ft 11 in
9 ft	14	7 11/16 in	13	11 ft 4 1/2 in	16	13 ft 9 in
10 ft	16	7 1/2 in	15	13 ft 1 1/2 in	18	15 ft 7 in
11 ft	18	7 5/16 in	17	14 ft 10 1/2 in	19	16 ft 6 in
12 ft	19	7 9/16 in	18	15 ft 9 in	21	18 ft 4 in
13 ft	21	7 7/16 in	20	17 ft 6 in	23	20 ft 2 in	Over 151 in: needs a landing (IRC)
14 ft	22	7 5/8 in	21	18 ft 4 1/2 in	24	21 ft 1 in	Over 151 in: needs a landing (IRC)

Heights in millimetres

An example with risers up to 190 mm and 250 mm goings. These are example limits, not a rule for any country: use the values that apply where you build.

Risers, treads and run by height in millimetres
Rise	Risers (≤ 190 mm)	Riser height	Treads	Run at 250 mm
2400 mm	13	184.6 mm	12	3000 mm (3.000 m)
2600 mm	14	185.7 mm	13	3250 mm (3.250 m)
2800 mm	15	186.7 mm	14	3500 mm (3.500 m)
3000 mm	16	187.5 mm	15	3750 mm (3.750 m)
3200 mm	17	188.2 mm	16	4000 mm (4.000 m)
3500 mm	19	184.2 mm	18	4500 mm (4.500 m)
4000 mm	22	181.8 mm	21	5250 mm (5.250 m)

Ceiling height is not the rise

A "9 ft ceiling" is measured floor to ceiling inside one storey. The stair has to climb from floor to floor, which adds the floor structure above: joists, subfloor and flooring. With 2x10 joists (9 1/4 in), 3/4 in subfloor and 3/4 in flooring that is 10 3/4 in, so a 9 ft ceiling becomes a 118 3/4 in rise, not 108 in. Always measure the actual rise before planning.

When the table says "needs a landing"

The IRC limits one flight to 151 in (12 ft 7 in) of rise between floors or landings (2024 R318.7.3), so 13 ft and 14 ft rises have to be split. The stair landing calculator splits them into two flights, straight or L-shaped.

For your exact height

The table rounds to the nearest 1/16 in. Your floor-to-floor height will rarely be a whole number of feet; use the stair calculator with your measurement to get exact risers, treads, run and a to-scale drawing.

Questions people ask

These are questions Google showed under "People also ask" for related searches (checked 2026-10-24), answered here with the same tested formulas the calculators use.

How many stairs are in 12 feet height?

For a 12 ft (144 in) floor-to-floor rise and risers no taller than 7 3/4 in: 144 ÷ 7.75 = 18.6, so 19 risers of about 7 9/16 in and 18 treads. With 10 1/2 in goings the run is 15 ft 9 in. A 12 ft rise is still within the IRC 151 in single-flight limit.

How long do stairs need to be for 10 foot ceilings?

With a 10 ft ceiling the rise is usually more than 10 ft, because the floor structure above adds to it. With 2x10 joists, subfloor and flooring (about 10 3/4 in) the rise is 130 3/4 in: 17 risers and 16 treads, so a 14 ft run at 10 1/2 in goings, plus a landing at the bottom (at least 36 in deep under the IRC).

What is the formula for calculating steps?

Risers = total rise ÷ maximum riser height, rounded up. Riser height = total rise ÷ risers. Treads = risers − 1 when the upper floor is the top step. Run = treads × going. The table above applies it to common heights; the formula guide shows every step with numbers.