Don't like ads? Go Ad-Free Today 

Stair Rise & Run Calculator

DeveloperMath

ADVERTISEMENT · REMOVE?

INPUT

Auto Process

OUTPUT

Client Side

Metric	Value
Number of steps (risers)	-
Number of treads	-
Riser height (each)	-
Tread depth (each)	-
Total run	-
Stair angle	-
Comfort rule (2R + T)	-
Code compliance	-

Summary

Enter a total rise to calculate the stair layout.

ADVERTISEMENT · REMOVE?

Guide

Stair Rise & Run Calculator

Design a code-compliant staircase from a total floor-to-floor rise and an optional total run. The calculator picks the optimal step count, computes each riser height and tread depth, and flags whether the result passes IRC residential or IBC commercial limits. It also draws a side-view SVG diagram and reports the stair angle and the 2R + T comfort rule.

How to Use

Pick imperial (inches) or metric (centimetres).
Enter the total rise — the exact floor-to-floor height you need to climb.
Optionally enter the total run if you are constrained by a stair opening length.
Pick a building code (IRC for homes, IBC for commercial, or no check).
Read the riser, tread, angle and compliance values from the results panel and check the diagram.

Features

IRC and IBC code checks – flags risers over 7.75 in (residential) or 7 in (commercial) and treads below 10 in or 11 in.
Step count optimization – iterates over valid riser heights and picks the option closest to the 2R + T = 25 in comfort rule.
SVG side-view diagram – redraws every time inputs change, including nosing overhangs.
Metric and imperial units – switching units rescales defaults for riser, nosing and can size.
Constraint-aware – if you give a total run, treads fill that distance; otherwise the calculator picks an ideal tread depth.

Typical Use Cases

Home renovations – plan a basement or attic staircase against IRC limits.
Deck and porch stairs – match existing floor heights to a clean step count.
Commercial fit-outs – validate stair geometry against IBC before framing.
Rough cost estimates – count risers and treads before cutting stringers.

 FAQ

What is the 2R + T comfort rule?

The Blondel comfort rule says 2 × riser height plus tread depth should land between about 24 and 25 inches. It keeps stride length consistent as people step up, so the stair feels natural to climb whether the steps are short and steep or long and shallow.
How do IRC and IBC limits differ?

The International Residential Code caps risers at 7.75 inches and requires treads of at least 10 inches, which suits steeper home staircases. The International Building Code is stricter for commercial and public buildings: risers up to 7 inches and treads of at least 11 inches, producing a gentler slope that is safer in high-traffic areas.
Why is the number of treads one less than the number of risers?

A staircase always starts on a landing and ends on a landing. The top landing is the floor above, so the last riser has no tread in front of it — the floor itself serves as that surface. That is why a stair with N risers has N − 1 treads between the two landings.
What does tread nosing do?

Tread nosing is the part of the tread that overhangs the riser below it. A small overhang of about an inch lengthens the effective stepping surface without adding to the stair's total run, making the stair easier and safer to descend because the ball of the foot has more contact area.