BIAB Water Calculator
Calculate your total water volume needed for Brew-In-A-Bag (BIAB) brewing. This helps ensure you hit your target batch size after accounting for grain absorption, boil-off, and kettle losses.
Enter your brew day parameters below and click “Calculate Water”
Understanding BIAB Water Needs
Brew-In-A-Bag simplifies all-grain brewing by mashing and lautering in a single vessel (your boil kettle) using a large grain bag. Calculating your water accurately is key:
- Target Batch Size: This is the amount of wort you want in your fermenter. All other calculations work backward from this.
- Grain Absorption: Grain soaks up water like a sponge. This water doesn’t make it to the fermenter. A typical absorption rate is around 0.12 gallons per pound (or 1 liter per kilogram) of grain, but this can vary.
- Boil-Off: During the boil, water evaporates. The rate depends on your kettle’s geometry, the vigor of your boil, and ambient conditions. You need to account for this lost volume.
- Kettle/Trub Loss: Some wort will always be left behind in the kettle, stuck to the sides, or absorbed by hops and trub (the sediment at the bottom).
The calculator sums these volumes to determine the Total Water Needed (also known as strike water for BIAB) to start your brew day. It also estimates your pre-boil volume after mashing and removing the grain bag.
Full Volume Mash: For BIAB, you typically use all your calculated water for the mash (a “full volume mash”). There’s no separate sparge step.