This document discusses methods for calculating rainfall intensity. It introduces the Talbot, Ishiguro, and Mononobe formulas which can be used to calculate intensity based on rainfall amount and duration. The Talbot formula is commonly used because its constants can be empirically determined. The Mononobe formula can calculate intensity using daily rainfall amounts when short duration data is unavailable. An example calculation using the Mononobe formula to find a 2-year intensity for a 1 hour duration is also provided. Finally, intensity-duration-frequency curves which relate these factors are mentioned.