Stair Calculator & Stringer

Stair Calculator & Stringer plans a stair from one number: the total rise from finished floor to finished floor. It proposes up to three stairs that fit the rule set you choose, draws them to scale and gives you the stringer marks to cut.

▶ ONE NUMBER IN, STAIR OPTIONS OUT
Enter the total rise in inches (108, 108 1/2 or 9' 0 1/2") or millimetres. You get up to three options side by side, each with:
• number of risers, riser height and going (tread depth)
• stair angle and the floor length it takes
• 2R + G, with a note whether it sits in the usual comfort range
The outlined card is the one closest to a comfortable step. Add the space you have and only the options that fit are shown; if none fits, the app tells you how much length the shortest allowed stair needs.

▶ STRAIGHT, L AND U STAIRS WITH A LANDING
Pick a straight flight or a quarter-turn (L) or half-turn (U) stair with one landing. The plan view is drawn to scale: move treads from one flight to the other and turn the stair left or right. The side view shows both flights and the landing.

▶ STRINGER MARKS FROM ONE POINT
Every cut height is measured from the same point, the seat of the stringer on the floor, so small errors do not add up step by step. Enter the tread thickness and any floor finish that is not laid yet, and every mark moves with it. Boards are listed at their actual size (2×10 = 9¼", 2×12 = 11¼", 45×220 and 45×245 mm), and the app shows how much wood is left under the cuts.

▶ CHECK AGAINST THE RULES WHERE YOU BUILD
Choose the rule set: US IRC 2021, Canada NBC 2020, England Approved Document K, Australia NCC 2022, Germany DIN 18065, Spain CTE DB-SUA, Netherlands Bbl, Poland WT or Japan's Building Standard Law Enforcement Order — or no rule set. The app checks only the riser, going, pitch and 2R + G numbers each document gives for a private stair in one dwelling, and names the document and clause. Headroom, width, handrails, nosings and landing size are not evaluated. The Code limits page lists every number it uses.

▶ PROJECTS
Save a stair with its name and reopen it later. Projects saved in the earlier version are carried over.

▶ GOOD TO KNOW
A planning aid: confirm the final dimensions with your builder or building department.

Works offline, no account. Supported by ads: an ad may appear when you open the app, a banner is shown at the bottom, and a full-screen ad may follow a saved project. Sharing a stair as text can be unlocked for 24 hours by watching an ad.