How is efficiency defined on the calculator? Kelsey August 26, 2020 12:28 The Grainfather recipe creator uses Brewhouse Efficiency to calculate the parameters of your recipe. Related articles My beer has finished fermenting but is cloudy, what should I do? Is the 'batch volume' the final, end amount I'll finish up with? How can I improve my efficiency? Where do I enter my mash water and sparge water volumes? What is BU/GU?