Last updated July 28, 2026
STAIRCAL works out stair riser and run dimensions from a floor-to-floor height. Give it the height and it reports the calculations — how many risers, what each one measures, and the going that goes with it.
It is by John Charles Vogt of Kennedy Associates, Architects, in St. Louis, Missouri.
It is imperial, and it rounds to the eighth of an inch
Not a caveat so much as the whole design. The routine has a dedicated helper whose only job is rounding a number to the nearest eighth of an inch, and it reports heights in feet and inches.
That is exactly right for an American architect in the era it was written, and exactly wrong for a metric drawing. There is no unit setting to change — the eighth-inch rounding is arithmetic baked into the calculations, not a display preference.
For Australian work this is a reference rather than a tool. The logic is sound and readable if you want to write a metric equivalent, but running it on a job dimensioned in millimetres will give you answers rounded to fractions of an inch.
It knows about the code
The detail that lifts this above a calculator. If the height you give it exceeds twelve feet, it warns you: a single run of over twelve feet is not permitted by most codes.
That is a landing requirement — a stair rising more than a certain height in one flight needs a break in it — and the exact figure varies by jurisdiction. The point is not the number, which you should check against the code you are working to. The point is that somebody who used this daily thought to put a warning in, because getting it wrong means redesigning a stair after it has been drawn.
Treat it as a prompt to check rather than as compliance advice. Australian requirements for riser and going dimensions, and for the maximum rise between landings, are set out in the National Construction Code, and they are not the American ones.
Command reference
The command is STAIRCALC, with a C on the end — the file and the download are both called Staircal without it.
Check it loads before you rely on it
An honest note. Two of the function definitions in this file have what look like descriptive comments sitting directly after the function name without the semicolon that would mark them as comments — lines reading “**** ROUND TO EIGHTH INCH ****” and similar.
Whether that stops the file loading depends on how your release’s AutoLISP reader handles those tokens. It may load and run without complaint. It may not. Load it in a scratch drawing and confirm the command is available before you plan a stair around it, and if it refuses, adding semicolons to those two lines is the fix.
How to load it
Unzip Staircal.zip and load STAIRCAL.LSP with APPLOAD. No support files. Our AutoLISP guide covers loading.
Step-by-step usage
- Load the file and confirm the command is recognised.
- Type STAIRCALC.
- Give it the floor-to-floor height. It reports that height back in feet and inches so you can check it took the number you meant.
- Read the calculations, and check the riser and going against the code you are working to.
Compatibility notes
No date in the file; version 1.0. It calculates and prints rather than drawing, so nothing in your drawing is at risk from running it — the risk is in trusting an imperial answer on a metric job.
Plain AutoLISP with no dialog boxes and no Express Tools calls, so nothing requires the full product; LT users on LT 2024 or later, the release that brought AutoLISP to LT, should be able to run it, subject to the loading question above. See what runs on AutoCAD LT.
Download
| Name: | Stair Calc |
| Description: | Stair riser and run calculations. |
| Type: | AutoCAD AutoLISP Routine |
| Author: | John Charles Vogt |
| File Size: | 3 Kb |
| Cost: | Free |
| Worked on: | AutoCAD |
| Download File: | Staircal.zip |
Related routines
- Spiral staircase — draws a stair in 3D rather than calculating one.
- ArchLisp — includes two stair drawing commands.
- WALLSECT — another architectural routine of the same vintage.