Notchline: Stair Calculator

Mufatech

In-app purchases

About this app

Notchline is a stair calculator that starts from the hole you have. Type the floor-to-floor height and, if you know them, the opening and the room you can give up. It finds the stairs that fit, checks each one against your stair code rule by rule, and lays out the stair stringer. Then it does the roof: a rafter calculator that works from any two numbers you can measure, with the birdsmouth checked. Pay once, no ads, works offline.

FIT THE HOLE
Most apps ask for the riser count or the run, then leave you to try numbers until the headroom works. Notchline goes the other way. Give it the height, the room along the stair, the room across, the opening and the floor depth. It tries a straight run, a stair with a landing, L and U stairs, quarter-turn and half-turn winders and a spiral, keeps the ones that fit and pass every rule plus headroom under the opening, and puts the most comfortable step first. If nothing fits, it tells you what would and by how much: more room along the stair, a longer opening, more headroom. If the opening isn't cut yet, it gives you the opening length you need.

THE INSPECTOR SHEET
Every rule of the code, one line each: the clause number and edition, the limit, your stair's number and a plain verdict, within limits or over by how much, with the smallest fix ("16 risers of 6 13/16 in"). IRC 2021, 2024 and 2018 and IBC in the US, NBC 2020 in Canada, Approved Document K in England, and the stair rules of Germany, France, the Netherlands, Spain, Italy, Australia and Türkiye. Rules taken from secondary sources are labelled. Pro prints it as a one-page PDF and checks the same stair against a second rule set side by side.

THE ROOF FROM WHAT YOU CAN MEASURE
Any two of run or span, rise, pitch and rafter length give you the rest. Values that don't agree are flagged, never overwritten. Pitch in x/12, degrees or percent. Add the overhang, rafter depth and seat cut and the birdsmouth is checked against a quarter of the rafter depth, on wood or masonry. No pitch on the plans? Lay the phone on the rafter, read it, turn the phone end for end and read again.

FOR THE STAIR YOU BUILD
• Rise and run in feet, inches and sixteenths, or mm and cm. A keypad with a feet key and one-tap fractions.
• Riser height, tread depth, total run, stringer length, angle, 2R + G and headroom, each with the formula and your numbers under it.
• Stringer layout: framing square settings, the drop at the first riser for tread and finish, the throat left in the board, board length.
• Deck stairs work the same way: total rise from the deck to the ground, then risers, treads and the stringer.
• Job card: one picture with the drawing, the numbers and the verdict, for the client, a coworker or the lumber yard.

FREE
Straight stairs with every number, your country's code check on screen, headroom, what would make it fit, stringer numbers, the common rafter with overhang and the birdsmouth check, the pitch gauge, unlimited jobs, backups, the job card, light, dark and high-contrast themes.

PRO, ONE PAYMENT
Stairs with a landing, L and U stairs, winders and spirals in the search; the same stair against a second code; the inspector sheet as a PDF; the stringer drawn with the square and every mark; hip rafter, valley and jack rafters with their cuts, also for unequal pitches. Try Pro free for 7 days. Nothing renews, no card. When Pro ends, every job stays readable, editable and exportable.

TRY IT ON SAMPLE JOBS
"Explore with sample jobs" opens a basement stair, a loft stair in a tight room and a garage roof. Remove them in one tap.

In English, Deutsch, Français, Nederlands, Italiano, Español, Português, Polski and Türkçe. No sign-up and no permissions. Nothing leaves your phone except a purchase through the store.

Results are design aids. Check the current rules with your local building authority before you build.

No account, no subscription, works offline.

What’s new

First release.
• Fit the hole: the stairs that fit your opening, height and room, ranked
• Inspector sheet: every rule with clause, limit, your value and the fix
• Roof from any two values, birdsmouth check and a phone pitch gauge
• Stringer layout, job card, feet-inch keypad
No account, works offline. A number looks wrong? Write to [e-mail]