Stair Planning Guides
Three in-depth guides behind the calculators. Pick the one that matches where you are in the project, or follow them in order.
Which guide do you need?
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If…
You are about to plan a new stair, or replace one, and need the starting number.
How to measure total rise
Where to measure, finished vs unfinished floors, sloping floors, and the flooring mistake that breaks the top step.
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If…
You have a height and want to understand or check the numbers a calculator gives you.
Rise and run formulas
Every formula with substituted numbers in inches and millimetres, what one more riser changes, fitting a fixed space, rounding without drift.
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If…
You need to know which rules apply and what the key limits are.
Stair code requirements
IRC, IBC, ADA and OSHA: who each covers, the key dimensions with 2024 and 2021 section numbers, and how to find your local rules.
A sensible order for a whole project
- Measure the total rise where the stair will land, allowing for flooring that isn't down yet.
- Plan the stair in the stair calculator (or the deck stair calculator outdoors). Compare at least two riser counts against your space.
- If anything in the result surprises you, check it by hand with the rise and run formulas.
- Read how the codes apply, then confirm the edition and any amendments with your building department.
- Lay out and cut with the stringer calculator, marking each notch from the first, not from the previous one.
Common questions, and where each is answered
Stair calculator
- How many stairs are in 9 feet height?
- How many stairs do you need for a 10 foot ceiling?
- What is the 7-11 rule for stairs?
- How to calculate staircase length?
- What are the parts of a staircase called?
Stringer calculator
- What is the stringer on stairs?
- What is the formula for stair stringers?
- Do I need 2x10 or 2x12 for stair stringers?
- How long is 2x12 for a 5 step stringer?
- What is the 27 rule for stair stringer dimensions?
Deck stair calculator
- What is the ideal rise and run for deck stairs?
- How many steps for a 24 inch rise on a deck?
- How many steps for a 27 inch rise?
- How to build exterior deck stairs?
Stair angle calculator
- How do you calculate the angle of stairs?
- What is the standard angle of stairs?
- Why is 37 degrees the best angle for stairs?
- How to cut a handrail for stairs?
Rise and run formulas
- How to calculate rise and tread in staircase?
- What is the ideal rise and run for stairs?
- Is an 8 inch stair riser too high?
Stair code requirements
How these guides are written
Every worked number in the guides comes from the site's tested calculation engine or is re-derived in an automated test, and every code value cites its edition and section. See the methodology, the sources and the editorial policy.