Sparge Water Calculator

This calculator works backward from your desired pre-boil kettle volume to tell you how much sparge water to add during an all-grain brew day. It starts with grain absorption: your grain weight multiplied by an absorption rate (in quarts per pound, default 0.125, the standard rule of thumb equivalent to 0.5 L/kg) tells you how much of your mash water the grain itself will soak up and never release into the kettle. Subtracting that absorbed volume from your mash water volume gives the first runnings — the liquid that drains free before any sparging begins. The gap between that first-runnings volume and your target pre-boil volume is the sparge water you need to add, floored at zero so the calculator never asks you to remove water.

It also reports a fixed recommended sparge temperature of 168°F, the standard target because it's hot enough to keep the wort's residual enzymes rinsing efficiently and the sugars flowing freely, but not so hot that it starts pulling tannins out of the grain husks (a common source of astringency in home-brewed beer). Total water needed simply adds mash water and sparge water together for a shopping-list figure. The main thing to watch is that this treats absorption and lautering as perfectly efficient — real system dead space, chiller losses, and boil-off aren't part of this particular calculation, so pair it with your own historical brew-day losses if your actual pre-boil volumes tend to run short or long of the number here.