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Trub loss is the wort that stays behind in the kettle when you transfer to the fermenter, the hot break, cold break, and hop material that settles or floats at the bottom and top of the kettle after chilling. Accounting for trub loss is essential for recipe scaling: if you’re targeting 5.5 gallons in the fermenter but you consistently leave 0.5–1 gallon of trub in the kettle, your pre-boil volume needs to be set to compensate. The calculator below helps you determine how much wort you lose to trub and how to adjust your recipe targets accordingly.
Trub Loss Calculator
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What makes up trub
Hot break forms during the boil, proteins and polyphenols coagulate in the boiling wort, forming large flocs that can be seen swirling in the kettle. Whirlfloc or Irish moss (added in the last 10–15 minutes of the boil) promotes hot break formation and aggregation into larger, easier-to-separate particles. A vigorous rolling boil for at least 60 minutes is necessary for good hot break development.
Cold break forms when wort is rapidly chilled from boiling to pitching temperature, proteins that were soluble at boiling temperature crash out as fine particles. Good cold break requires fast chilling (use a wort chiller to drop from 212°F/100°C to pitching temperature quickly rather than letting the wort cool slowly overnight). Rapid chilling produces more visible cold break particles, which settle in the kettle rather than being transferred to the fermenter.
Hop material, whole hops, hop pellet debris, and dry hop additions, adds to trub volume significantly. Highly hopped IPAs with multiple hop additions can leave substantial hop trub in the kettle. Hop stands and whirlpool additions produce less compacted trub than pellet additions stirred into a boil.
Typical trub loss by brewing setup
| Setup | Typical trub loss | Notes |
|---|---|---|
| Basic homebrew kettle, no whirlpool | 0.5–1.0 gallon | Most variable; depends on technique |
| Whirlpool technique | 0.25–0.5 gallon | Compact cone of trub in center |
| Conical fermenter with trub dump valve | Transferred with wort; separated later | More flexible but requires extra step |
| Bag (BIAB) system | 0.1–0.3 gallon | Less hop material in wort |
| High-hop IPA (4+ oz whole hops) | 1.0–1.5 gallons additional | Volume depends heavily on hop form |
Measuring and accounting for your trub loss
The most accurate approach: after a brew session, measure how much wort remains in the kettle after transferring to the fermenter. This is your actual trub loss. Track this over several batches to establish your system average. In your recipe software, enter this value as “kettle trub loss” or “fermenter dead space”, the software will add the trub loss back to the pre-boil volume target automatically. If you don’t use software: add your trub loss directly to your target fermenter volume (e.g., targeting 5.5 gallons in fermenter + 0.75 gallons trub = 6.25 gallons post-boil volume target).
Common Questions
Should I transfer trub to my fermenter?
Leaving trub behind in the kettle produces cleaner-fermenting wort with fewer off-flavor precursors, lipids and proteins in hot trub can contribute staling and off-flavors over time. However, some trub in the fermenter is not catastrophic, active fermentation can mask minor trub-derived off-flavors, and the cold break contains some yeast nutrients. The practical middle ground: use a whirlpool to compact trub in a cone and transfer the clear wort above it, leaving the compacted trub behind. This captures more wort volume than being very conservative, while leaving the worst trub in the kettle. For a 5-gallon hoppy ale where every drop matters, accepting a slightly cloudier transfer is better than leaving a gallon of wort behind.
