Slope and Angle Converter

[Please note first] This app rewrites a slope figure in another notation, and nothing more. It is not a general sine, cosine and tangent calculator, and it will not work an angle out from the lengths of two sides. It cannot measure a slope by tilting your device, and it holds no target figures and no judgement about regulations or standards. ────────── ∠ Slope and Angle Converter - that "10%" is not 10 degrees The "10%" on a road sign works out at about 5.7 degrees. Percent asks how far you rise over a run of 100, which is not an angle. Enter one number, pick two units. Six units, in any direction. ■ One slope, three notations Roofs use sun, roads use percent, ramps use a fraction such as 1 in 12. 4 sun = 40% = 1 in 2.5 is a single slope, about 21.8 degrees. Enter one number and the other five units line up at once. Know any one of them and you can read the rest on the spot. ■ 45 degrees is exactly 100% Percent has no ceiling. At 60 degrees it reaches 173.2051%. Read 100 as a maximum and the steepest signs stop making sense. ■ 90 degrees cannot be written as a slope A vertical face has no run for the rise to stand against, so percent, sun and the fraction all fail. Flat ground at 0 degrees has no n for "1 in n". Both come back as a dash, with a line saying why. ■ Sun is a ratio, not a length A roof written as 4 sun rises 4 for every 10 of run. It shares its name with an old Japanese length unit and is not the same thing. A note saying so sits beside the answer every time. ■ Only 1 in n reads bigger for gentler Enter the n of "1 in 12", which is 12. The other five grow as the slope steepens; this one runs the other way. ■ Radians and grads A radian counts radius lengths laid round the arc, and 180 degrees is pi of them. It carries no unit at all, which sets it apart from the other five. A grad splits the right angle into 100, so 90 degrees = 100 grads, and one grad is exactly 0.9 degrees. Surveyors use it. ■ Six units Degrees, radians (rad), grads (grad), percent slope (%), sun (roof pitch) and the fraction 1 in n. ■ Good for ▪ Putting a figure on the percent shown on a road sign or a hazard map ▪ Seeing how steep a roof written as 4 sun actually is ▪ Checking whether 1 in 12 and 8.333333% on a drawing are the same slope ■ Things worth knowing (included in the app) ▪ 10% is not 10 degrees; it is about 5.7 ▪ 4 sun = 40% = 1 in 2.5 is one slope, about 21.8 degrees ▪ 45 degrees is exactly 100%, and 60 degrees reaches 173.2051% ▪ 90 degrees cannot be a slope; 0 degrees has no n for 1 in n ▪ A radian counts radius lengths; 180 degrees is pi of them ▪ A grad splits the right angle into 100, so 90 degrees = 100 grads ■ How the app is built ▪ A single screen and no settings page ▪ Nine common slopes, each one tap away ▪ Your last five entries are kept and can be tapped to restore ▪ One tap copies the result ▪ Japanese and English, following your device language ▪ No account needed. The conversion runs on your device and the number you type is never sent anywhere ────────── Note: this app rewrites a slope figure and nothing more. There is no general sine, cosine and tangent calculator, no way to get an angle from two side lengths, and no measurement by tilting the device. Recommended pitches for particular roofing materials, and any judgement about building regulations or accessibility standards, are out of scope.