Stair Calculators: Which One Fits Your Job
Four tools, one geometry engine. Start with the stair calculator unless you already know your stair and need a specific next step.
| Calculator | Use it when | You enter | You get |
|---|---|---|---|
| Stair Calculator | You know the floor-to-floor height and want the stair: how many steps, how tall, how long. | Total rise, the tallest riser you accept, the going. | Risers, treads, riser height, total run, angle, alternatives, informational code checks, a to-scale drawing. |
| Stair Stringer Calculator | You have a stair plan and need to cut the stringers. | The stair, plus tread thickness and the actual width of the board. | First-riser drop, framing-square settings, mark positions, throat depth, the shortest board, a template drawing. |
| Deck Stair Calculator | Steps from a deck down to the yard, especially on sloping ground. | Deck height at the edge, how the ground slopes, landing pad, deck boards. | Riser count solved at the real landing point, where the stair lands, stringer and board counts. |
| Stair Angle Calculator | You need the angle in degrees, or the run needed for an angle. | Riser and going, or total rise and run, or a target angle. | Angle, grade, rise-to-run ratio, a fitted step layout, published angle ranges for comparison. |
A typical order of work
- Measure the total rise at the spot where the stair will land.
- Plan the stair with the stair calculator (or the deck stair calculator outdoors), and compare a few riser counts against the space you have.
- Check the layout against your local code, starting from how stair codes apply.
- Lay out and cut with the stringer calculator.
All four calculators share the same tested engine and the same conventions. They are documented on the methodology page.
Not here yet
Headroom under a floor opening, multi-flight stairs with landings, and winder or spiral stairs need geometry models that are not finished to the standard of the tools above, so they are not published. If you need one, say so on the contact page. Requests decide what gets built next.