Minecraft wiki entry for Breaking, associated text: If a proper tool is used, the tool speed is further increased by the Efficiency enchantment. If the level of Efficiency is not 0, then the level squared plus 1 is added to the tool speed. For example, Efficiency I adds 2 to the value, while Efficiency V adds 26. The speed is also increased by (20×level)% per level of Haste, while Mining Fatigue decreases it by 70% for level I, 91% for level II, 99.73% for level III, and 99.919% for all other levels.