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Boil-Off Calculator

How much volume you'll lose, and when to stop boiling

During the boil, water evaporates but sugar stays. That concentrates your wort. Gravity goes up as volume goes down. This calculator tells you how much volume you'll end up with, or how long to boil to hit your target gravity.

Boil-Off

volume concentration

Pre-boil gravity came in low? Work out how much to boil down to concentrate and land on your target OG.

Post-Boil Volume
5.44gal
Boil Off
1.56gal
Est. Boil Time
75min
42.0 pts × 7 gal = 54.0 pts × 5.44 gal

How We Calculate It

Post-Boil Volume
Vpost=Vpre×GpreGtargetV_{post} = \frac{V_{pre} \times G_{pre}}{G_{target}}

Same conservation principle as dilution, in reverse. Water leaves, sugar stays, gravity concentrates.

If you know your boil-off rate (liters per hour), you can also calculate the boil time needed to reach your target. Typical boil-off rates are 3–5 L/hr depending on your kettle and burner.

See all the numbers come together in real time.

Build a full recipe

Related Topics

DilutionFigure out how much water to add to hit your target gravity.Gravity & ABVHow original gravity is built from your grain bill, and the path from OG to FG to alcohol.