Boil-Off Rate Calculator

How It Works

Boil-off rate varies significantly by system — typical ranges are 0.75-1.5 gallons per hour for a 5-gallon batch. Factors include kettle diameter (wider = more evaporation), burner intensity, humidity, and altitude. Knowing your exact boil-off rate is critical for hitting target volumes and gravities. Measure it by marking a dipstick or using a calibrated sight glass. A 60-minute vigorous boil is standard — it drives off DMS (dimethyl sulfide, a corn/cabbage off-flavor precursor from pilsner malt), isomerizes alpha acids from hops, sterilizes the wort, and helps proteins coagulate for clearer beer. Pre-boil gravity should always be checked: if it is too low, extend the boil; if too high, add water.