Chilling requirements (hours or units) are typically computed to estimate when fruit trees complete dormancy. This calculator allows both the use of a simple count of hours between two temperature thresholds, such as above 32F and below 45F, and the more complex Utah model (Richardson, Seeley, Walker 1977). Insufficient chill hours can result in delayed foliation, and reduced fruit set and quality. See Victoria BC or UC Extension for more complete introductions to chill units and formulas for simple and Utah types of chill units.