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Stair Rise and Run Calculator

Turn one total‑rise measurement into equal risers and runs that meet code — with the comfort rules (2R+T and Rise+Run) checked for you.

Checks IRC, IBC, OSHA & ADA Live 3D model & cut list Imperial & metric

16 steps 33.2°

Meets IRC 2021

Your stairs

Total rise

Finished floor to finished floor.

Target riser height

Stairs Calc rounds to a whole number of equal risers and keeps them within code.

Tread run (going)

The depth you step on, not counting the nosing.

Stair width

Stringer mount

Railings

Left side

Right side

Rail height

Top of the rail above the nosing line. Codes target 34–38".

A guard fills the side with your chosen infill — balusters, glass, cable, or horizontal bars. Renders live in 3D and is included in the .obj export.

Advanced inputs

Nosing

Tread thickness

Upper floor thickness

Headroom

Risers

Open risers leave a gap between treads — drawn live in the diagram. Some codes (ADA) require closed risers.

// 2D ELEVATION

Steps (risers)

15 treads

Riser height

7 3/16"

183 mm

Tread run

11"

279 mm

Stringer length

16' 8 15/16"

5.104 m

Stair angle

33.2°

Very comfortable

Total run

13' 8 3/4"

4.185 m

Min stairwell opening

10' 11 13/16"

3.348 m

Recommended board

2x12

throat 5 1/4"

Board to buy

17' 8 15/16"

5.409 m

Comfort

90 / 100

Very comfortable

Blondel pass
Rise + Run pass
Ideal angle pass

Cut list & framing square

Materials

Item	Qty	Detail
Stringers	3	2x12 cut to board length
Treads	15	tread depth 304 mm × 914 mm wide
Risers	16	riser height 183 mm × 914 mm wide
Fasteners	180	structural screws / nails (≈4 per tread-to-stringer joint)

Framing-square settings

Rise on tongue: 7 3/16"
Run on body: 11"
Recommended board: 2x12
Throat: 5 1/4"
Board length: 17' 8 15/16"
Stringers: 3

Per-step running measurements

Step	Cumulative rise	Cumulative run
1	7 3/16"	11"
2	14 3/8"	21 15/16"
3	21 9/16"	32 15/16"
4	28 3/4"	43 15/16"
5	35 15/16"	54 15/16"
6	43 1/8"	65 7/8"
7	50 5/16"	76 7/8"
8	57 1/2"	87 7/8"
9	64 11/16"	98 7/8"
10	71 7/8"	109 13/16"
11	79 1/16"	120 13/16"
12	86 1/4"	131 13/16"
13	93 7/16"	142 13/16"
14	100 5/8"	153 3/4"
15	107 13/16"	164 3/4"
16	115"	175 3/4"

Cut the bottom riser shorter by 1" so every finished riser stays equal.

Save & compare designs Show

Save the stair you're looking at, tweak the inputs, save another, then compare them side by side — comfort, code, and key dimensions at a glance.

Estimate the cost $1,139–$1,709

Material

Include railing

Labor 50%

Stringers (3)	$176
Treads (15)	$270
Risers (16)	$144
Fasteners & hardware	$25
Railing	$335
Labor	$475

Low

$1,139

Estimate

$1,424

$89/step

High

$1,709

Rough order-of-magnitude only. Lumber, fastener and labor prices swing by region and season — the low–high band reflects that spread. For a line-item breakdown with editable prices, open the stairs cost calculator.

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Quick answer

What is the rise and run of stairs?

Rise is the vertical height of one step and run is the horizontal tread depth. The most comfortable step is about a 7″ rise with an 11″ run — the "7‑11 rule" — which satisfies both comfort formulas (rise + run ≈ 17″–18″ and 2×rise + run ≈ 24″–25″). The US code caps the riser at 7¾″ and the tread at no less than 10″.

Ideal rise: 7″
Ideal run: 11″
Max riser (IRC): 7¾″
Min tread (IRC): 10″

What rise and run mean

Rise is the vertical height of one step; run (also called the going) is the horizontal depth you step on, measured nosing-to-nosing. The calculator takes your total rise, divides it into a whole number of equal risers — which is what building codes require — and pairs them with your chosen run. It then checks the 3⁄8″ uniformity rule and scores the result on the comfort meter above. Once the rise and run are set, the stair stringer calculator turns them into cut marks, and the stair angle calculator shows the resulting pitch.

The comfort rules

Three classic rules describe a comfortable step, and Stairs Calc checks all three:

Blondel (2 × rise + run = 24″–25″) — matches a natural stepping cadence.
Rise + run = 17″–18″ — a simple balance of effort and reach.
The 7-11 rule — a 7″ rise with an 11″ run satisfies both and lands around a comfortable 32–33° angle.

Stair formulas

Number of risers: N = round(total rise ÷ ideal riser)
Round to the nearest whole number, then divide the rise back by N for the exact, equal riser height.
Riser height: riser = total rise ÷ N
Treads: treads = N − 1
The upper floor acts as the top step.
Total run: total run = (N − 1) × run
Stringer length: stringer = √(total rise² + total run²)
The hypotenuse of the staircase triangle (Pythagoras).
Stair angle: angle = atan(rise ÷ run)
The pitch of one step.
Minimum stairwell opening: opening = ((floor thickness + headroom) × total run) ÷ total rise
Throat: throat = board width − (rise × run) ÷ √(rise² + run²)
Keep at least 3½″ of solid wood behind the notch.
Comfort — Blondel: 2 × rise + run = 24″–25″
The classic stepping-cadence rule.
Comfort — Rise + Run: rise + run = 17″–18″
Comfort — Product: rise × run ≈ 70–75 in²

Worked example — a 9′-7″ total rise

Dividing by an ideal 7" riser gives 16 risers, so each riser is 7³⁄₁₆". With a 11" run there are 15 treads, a total run of 13′-8¾″, a stringer length of 16′-9″, and an angle of 33.2° — very comfortable and within IRC limits.

Stair terminology

Total rise: Vertical distance from the lower finished floor to the upper finished floor.
Riser height: The vertical height of a single step; every riser must be equal within 3⁄8 in.
Run (going): The horizontal depth of one step, measured nosing-to-nosing, not counting the overhang.
Tread: The horizontal board you step on; its depth equals the run plus the nosing.
Nosing: The lip of the tread that overhangs the riser below; ¾–1¼ in in the IRC.
Riser (board): The vertical board that closes the gap between two treads on a closed-riser stair.
Stringer: The notched board that carries the treads and risers; usually a 2×12.
Throat: The solid wood left behind a stringer notch; keep it at least 3½ in.
Stringer length: The diagonal length of the stringer, the hypotenuse of total rise and total run.
Total run: The horizontal distance the whole flight covers, floor to floor.
Number of risers: How many equal steps the flight has; total rise divided by target riser, rounded.
Headroom: Vertical clearance measured plumb above the nosing line; minimum 6 ft 8 in (IRC).
Landing: A flat platform that breaks a flight or changes its direction.
Stringer mount (standard vs flush): Whether the top tread sits one riser below, or level with, the upper floor.
Walkline: The path 12 in in from the inside of a turn, where winder tread depth is measured.
Winder: A wedge-shaped tread that turns a staircase without a flat landing.
L-shaped stairs: A staircase with a 90° turn, made with a quarter landing or winders.
Spiral staircase: A helical stair whose wedge treads wind around a central column.
Tread angle (rotation): The plan-view angle each spiral or winder tread sweeps around the center.
Stair angle (pitch): The slope of the flight in degrees; comfortable stairs sit around 30–37°.
Stair width: The clear walking width of the flight; IRC minimum 36 in above the handrail.
Handrail: The graspable rail along a stair; code height 34–38 in above the nosing line.
Guardrail (guard): The barrier protecting an open edge; minimum 36 in high (IRC residential).
Baluster (spindle): The vertical infill posts of a railing; gaps must reject a 4 in sphere.
Newel post: The sturdy anchor post at the end or turn of a railing.
Cable railing: A guard infilled with tensioned horizontal cables instead of balusters.
Glass railing: A guard infilled with tempered glass panels instead of balusters.
Stairwell opening: The hole framed in the upper floor that the staircase rises through.
Blondel formula (2R + T): The comfort rule that twice the rise plus the run should equal 24–25 in.
Flight: An uninterrupted run of steps between floors or landings.
Finished floor: The walking surface after flooring is laid, from which total rise is measured.
Waist slab: The inclined structural slab beneath cast concrete stairs.
MET value: A metabolic-equivalent rate used to estimate calories burned climbing stairs.
Bullnose step: A rounded starting step, wider than the flight, that wraps past the newel.
Volute: The spiral scroll that terminates a handrail over the bullnose step.
Half-landing: A full-width landing where a stair reverses 180° in a U-shaped flight.
Stair soffit: The finished underside of a staircase or its landing.
Balustrade: The complete railing assembly: handrail, balusters, and newel posts together.
Kite winder: The central, kite-shaped winder tread at a 90° turn made of three winders.
Nosing return: The mitred end-cap that finishes an open-side tread nosing flush with the skirt.
Open-riser stair: A stair with no riser boards, leaving a gap between treads; gap rejects a 4 in sphere.
Plumb cut & seat cut: The vertical and horizontal end cuts that let a stringer meet the floors.
Handrail extension: The code-required horizontal run a handrail must extend past the top and bottom steps.
Skirt board (string board): The trim board against the wall that the treads and risers butt into.
Ramp slope: The rise-to-run ratio of an accessible ramp; ADA caps it at 1:12.

[ 01 / 01 ] FAQ

Frequently asked questions

What is rise and run on stairs?

Rise is the vertical height of one step (the riser); run, or going, is the horizontal depth you step on, measured nosing‑to‑nosing and not counting the overhang. Total rise and total run are the same dimensions for the whole flight.

What is the 7‑11 rule?

The 7‑11 rule says the most comfortable step is about a 7″ rise with an 11″ run. It satisfies both comfort formulas (rise + run ≈ 17″–18″ and 2 × rise + run ≈ 24″–25″) and produces a pitch of roughly 32.5°.

What is the maximum variation between steps?

Risers and runs must stay within 3⁄8″ of each other across the flight. The reason is safety: your body learns the step size on the first stair, so an uneven step becomes a trip hazard. Stairs Calc keeps every riser and run equal.

What is a comfortable stair angle?

A comfortable flight falls between 30° and 37°. A 7‑11 stair sits right in the sweet spot at about 32.5°.

Related stair calculators

Stair Stringer Calculator Get the exact stringer length, throat depth, recommended board size, and a step‑by‑step cut layout with framing‑square settings — then print a full‑scale template. Stair Angle Calculator Enter rise and run to get the exact stair angle in degrees and slope — and see instantly whether it falls in the comfortable 30–37° range. Stairs Calculator Enter one measurement — your total rise — and get a complete, code‑compliant stair layout with a 3D diagram, stringer cut list, and printable template. Free, instant, in inches or millimeters. Stair Code Requirements (IRC, IBC, OSHA, ADA) Everything the stair calculators check, explained: the exact riser, tread, headroom, width, handrail and guard limits — for homes, commercial buildings, workplaces and accessibility.

Written by the Stairs Calc editorial team. Methodology and code references: see our methodology.

Built and maintained by builders, drafters and engineers who plan stairs for a living — every code limit is transcribed from the published standard and cited to its exact section.

Last reviewed 2026-06-20 against IRC 2021/2024

Stairs Calc gives accurate geometry and checks it against published building-code limits, but results are estimates for planning. Codes are adopted and amended locally and change over time. Always confirm dimensions against your local adopted code and a licensed professional before you build.