Will the stair fit? Give us the height. We’ll work it out
The height from floor to floor in, the stair out: how many risers, how high each, how deep the treads, the pitch, the footprint, for straight, L-shaped, U-shaped, three-flight, curved and spiral stairs. Then open it in 3D, every tread and post at its real size, or tell uCAD’s AI the rest.
How it works it out
- Risers. The fewest that keep each one at most 18 cm (7″) high, all the same: the height divided by them. 2.80 m: 16 risers of 17.5 cm. A spiral allows 20 cm.
- The going. Two risers and a going make a comfortable stride of about 63 cm (25″) — the rule stair builders have used since Blondel: 17.5 cm risers, 28 cm treads.
- Treads. One fewer than the risers: the last riser goes up to the upper floor itself.
- Turns. A landing as deep as the stair is wide, or winders, which take a riser each and save room; the flights split evenly unless you say otherwise.
The codes' limits, for comparison
US homes (IRC)
Risers at most 7¾″, treads at least 10″; headroom 6′8″; at least 36″ wide; a handrail 34–38″ over the nosings.
UK homes (Approved Document K)
Rise at most 220 mm, going at least 220 mm, pitch at most 42°; 2.0 m headroom; handrails at least 900 mm; no gap a 100 mm sphere passes.
Spiral stairs (IRC)
At least 26″ clear; risers at most 9½″; headroom 6′6″.
The calculator aims at a comfortable stair, well inside these. Codes change and differ between places and between homes and public buildings: check the one that applies to yours.
Then see it in 3D
L-shaped
A landing or three winders at the corner.
U-shaped
Two flights side by side, a landing or winders.
Spiral
Round a column, headroom under every turn.
All of them: staircases for a house · U-shaped stairs · spiral staircases · metal stairs · stairs by floor height, from 2.40 to 3.40 m and 8 to 12 ft.
Tell us what you need. We’ll do it.
uCAD’s AI draws it in real sizes, and changes it when you ask.
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It will: we work out the steps from your floor height and show you.
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You say it, we draw it
No CAD to learn: write what you need the way you’d tell a builder or a designer.
Not right? Say so
“Move the sofa to the window.” “A metre wider.” Every change can be undone; nothing can break.
Free to try
Nothing to install: it opens in your browser. A new account tries the AI free.
Questions
Do I need to know CAD?
No. Say what you need and uCAD’s AI draws it; ask again to change it. The drawing tools are there if you’d rather do some of it yourself.
What does the AI cost?
A new account tries it free. After that it comes with uCAD Pro ($19.99 a month); building after a photo, a sketch or a plan is in uCAD Studio ($49.99 a month). Drawing by hand, importing and exporting stay free.
How exact is it?
Every part has its real size, and you can measure anything. If the AI gets a detail wrong, tell it, or fix it by hand.
What is the floor-to-floor height?
From the finished floor below to the finished floor above — not to the ceiling: add the thickness of the floor above, its screed and flooring.
Can I set the number of risers or the tread depth myself?
In the 3D stair, yes: Risers and Going stay “auto” until you type a number, and everything else follows.
What about the stringer length?
Open the stair and measure it with the tape measure, or pick the stringer: its size is in the panel. For a straight flight it is the diagonal of the run and the rise.
Is it free?
Yes, with no sign-up: the calculator, the 3D stair, changing it and exporting it.