# Water Volume Calculator

Brewing water volume is the total liters of water a batch requires, split between mash water and sparge water. In a sparge mash, mash water is grain weight times the water-to-grain ratio (typically 2.6 L/kg), and sparge water makes up the difference between the pre-boil volume and the first runnings, after subtracting grain absorption (roughly 1.04 L per kg of grain) and any mash tun dead space. In a full-volume (no-sparge or BIAB) mash there is no second addition: the mash carries the entire water bill, so it runs much thinner.

Know how much water you need before you start heating it, not after you run out halfway through the sparge.

HTML version: https://brewgravity.com/calculators/water-volume/

## Inputs

- **Target batch volume (L)** (min 0.1, step 0.5) — default: 19
- **Total grain (kg)** (min 0, step 0.1) — default: 5
- **Boil time (min)** (min 0, step 5) — default: 60
- **Boiloff rate (L/hr)** (min 0, step 0.1) — default: 3.8
- **Mash type** (Sparge / Full volume (no sparge / BIAB)) — default: sparge

## Outputs

- **total**: Total water needed
- **mash**: Mash water
- **ratio**: Mash ratio
- **sparge**: Sparge water
- **preboil**: Pre-boil volume
- **absorb**: Grain absorption
- **boiloffOut**: Boiloff

## FAQ

### How much water does grain absorb?

Roughly 1.04 liters per kilogram of grain (0.125 gallons per pound). This is water you will not get back — it stays in the spent grain. A 5 kg grain bill absorbs about 5.2 liters.

### What boiloff rate should I use?

Measure it on your own system — bring a known volume of water to a boil for an hour and measure what is left. Typical stovetop setups lose 3.5–4.5 liters per hour. Larger burners and wider kettles lose more.

### Can I skip the sparge?

Yes — that is brew-in-a-bag (BIAB), or any no-sparge mash. Set the mash type to full volume and the whole water bill goes into the mash, which works out to roughly 4–6 L/kg rather than 2.6. Efficiency is usually a few points lower.

### Does a full-volume mash change the strike temperature?

Yes, and this is the part people get caught by. A thinner mash has more water per kilogram of grain, so the grain pulls the temperature down less — a full-volume mash needs strike water several degrees cooler than the same beer sparged. Using a sparge strike temperature on a full-volume mash overshoots the rest.

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Source: https://brewgravity.com — Free water volume calculator splitting total brewing water into mash water, sparge water, grain absorption and boiloff from batch size, grain weight, boil time and boiloff rate.