What this is
StairStringerChart is a free, browser-based calculator for the layout work on a deck or a stair: stair stringers, baluster and picket spacing, deck joist and beam spans, rafters and board feet. Every page pairs a live drawing with a spec sheet you can take to the saw, and a reference chart you can print.
Everything runs in your browser. There are no accounts and nothing you type is sent anywhere.
Real tape fractions, hooked once
Shop work happens in sixteenths, so every length is shown as a tape-measure fraction first, with the decimal and millimetres beside it. When a value sits noticeably off a sixteenth, it carries a + or −, the way carpenters say "strong" or "light".
- Layouts come as running marks from a single hook of the tape, so a rounded sixteenth never compounds down a stringer or a rail.
- Sloped stair rails get marks along the rail: the level spacing divided by the cosine of the stair angle.
- The bottom riser is shortened by the tread thickness automatically, so the first step is not taller than the rest.
Where the numbers come from
The limits and tables are taken from published sources and checked by unit tests and a build-time verification script before every release:
- Stairs, guards and handrails: the 2021 International Residential Code, R311.7 and R312 (the 2024 IRC keeps these limits and renumbers the stair sections to R318).
- Deck framing: American Wood Council DCA 6-15, Prescriptive Residential Wood Deck Construction Guide: Table 2 joist spans, Table 3A beam spans, Table 4 posts and footings, and the stair figures (2x12 stringers, 5" throat, 6'-0" cut-stringer span, 18" spacing).
- Lumber sizes: the American Softwood Lumber Standard (PS 20) dry dressed dimensions.
- Comfort: Blondel’s 2R + T rule, the 7-11 stair and common shop practice, labelled as such.
What it is not
A calculator lays out what the code allows; it does not approve it. Codes are adopted and amended locally, span tables assume a 40 psf live load and No. 2 lumber, and nothing here sizes rafters for snow or covers hot tubs, roof loads or engineered lumber. Pull the permit, follow your inspector, and cut one stringer to test before you cut the rest.
Who runs it
StairStringerChart is an independent reference, a sibling of ScrewBoltChart. Found a number that disagrees with your code book? Write tocontact@stairstringerchart.com or use the contact page, and include the source so it can be checked and fixed.