The Drought Calculator is designed to be used by ranchers and range managers to get an early prediction of drought and forage growth potential. Precipitation during certain months in the growing season has a greater impact on forage growth than other months. By using field data from range research stations and long-term precipitation data, the weights or significance of monthly precipitation can be calculated. For example, precipitation in March might be less significant than in April which, in turn, might be less significant than May. As monthly precipitation values are added, the Calculator uses the weights for each month to estimate the impact of precipitation on forage growth. The Calculator uses simple, easy to acquire monthly precipitation data. The precipitation data can be acquired from an on-board database, from user collected data, or a combination of the two.