Choose the right calculator
Use the pitch calculator when rise and horizontal run are known. Use the converter when the slope is already expressed as degrees, percentage, rise per 12 or a multiplier. Use the triangle solver when exactly two right-triangle properties are known.
Use the rafter calculator for a theoretical common-rafter line, the area calculator for supported simple plan forms, the material estimator after area has been checked, and the Multi-section Roof Workbench when independently measured sections have different pitches.
A deliberate calculation chain
Do not start with material quantity when the geometry is uncertain. Confirm units and measurement endpoints, calculate pitch or factor, derive the supported line or area, then apply coverage and waste as separately recorded assumptions.
All tools explain geometry only. They do not produce structural design, cutting instructions, code approval, installation advice or a guaranteed order quantity.