Every trade writes slope differently — 1:12 for ramps, 2% for drainage, 30 degrees for a roof, 20 mm per metre for a shower tray. Enter what you have, get all of them, plus the ramp length and landing count.
Notes
The four ways of saying the same thing
A 1:12 ratio is 8.33 percent, is 4.76 degrees, is 83.3 mm of fall per metre. They describe the same slope. Ratio is common for ramps, percent for roads and drainage, degrees for roofs, mm per metre for plumbing.
Ratio is run over rise, not the reverse
1:12 means twelve along for one up. Writing it upside down turns a gentle ramp into an unusable one, and it happens more often than you would think.
Landings
Long ramps normally need level landings at intervals, and the maximum run between them varies by country and by use. Set the interval yourself from whatever applies to your job.
What this does not do
It converts geometry. Accessibility requirements, maximum gradients and landing rules are set by regulation where you are building, and this tool does not know them.