Roof Pitch to Angle Converter

A roof slope can be written four ways, and this tool moves between all of them. Pitch is rise-in-`12`, the framing-square language a roofer uses. Angle is the same slope in degrees, the way a phone inclinometer or a protractor reads it. Grade is the percentage a highway sign shows. Slope factor is the multiplier that turns flat footprint area into true roof area.

They are all the same underlying ratio, so converting is pure trigonometry. Type a pitch and the angle is the arctangent of rise over `12`; the grade is rise over `12` times `100`; the slope factor is the square root of rise squared plus `144`, divided by `12`. Type an angle instead and the pitch is the tangent of that angle times `12`. Type a grade and the pitch is the grade over `100` times `12`. Whichever field you edit, the other three follow instantly.

This is the quick reference you reach for when a plan calls out a `30`-degree roof and your framing square only speaks in twelfths, or when an app tells you the slope is `47` percent and you need to know whether standard shingles are rated for it. There is nothing to measure and nothing to order — it is a converter, so there is no diagram or print sheet, just the four equivalent numbers.