Brewer’s ToolboxBoil-Off Rate Calculator for Different Kettles by John Brewster June 4, 2025 by John Brewster June 4, 2025 5 minutes readYour boil-off rate is the volume of wort that evaporates per hour during the boil. For most homebrewing kettles, that’s 1–1.5 gallons per hour (3.8–5.7 L/hr), but I’ve measured rates as low as 0. Read more