How much water do you need for an all-grain batch?
Work backwards from the beer. You want a certain volume in the fermenter; the kettle keeps some behind; the boil evaporates some; hot wort is bigger than cold wort; the grain drinks some; the tun hides some. Add it all up and that's what you measure out on the morning:
Total water = batch + kettle loss (÷ shrinkage) + boil-off + grain absorption + tun deadspace
For 11 lb of grain on the default profile — 5.5 gal into the fermenter, 72% efficiency, a 60-minute boil at 1.25 gal/hr — that's 8.8 gal of water: about 4.4 gal to mash in and 4.4 gal to sparge. Metric, 5 kg into 21 L: 33.3 L total, 16 L strike and 17.3 L sparge. Every one of those numbers moves with your equipment, which is why this page reads them from your profile instead of asking again.
The brew-day water ledger, top to bottom
Two default profiles, so you can see where each drop goes:
11 lb · 5.5 gal batch · batch sparge
| Strike water | 4.38 gal |
| Sparge water | 4.39 gal |
| Total water | 8.77 gal |
| − grain absorption | 1.32 gal |
| − tun deadspace | 0.25 gal |
| = Pre-boil, cold | 7.2 gal |
| Pre-boil, hot in the kettle | 7.5 gal |
| − boil-off | 1.25 gal |
| = Post-boil, hot | 6.25 gal |
| Post-boil, cooled | 6 gal |
| − kettle loss | 0.5 gal |
| = Into the fermenter | 5.5 gal |
| − fermenter loss | 0.5 gal |
| = Into bottles or keg | 5 gal |
5 kg · 21 L batch · batch sparge
| Strike water | 16 L |
| Sparge water | 17.3 L |
| Total water | 33.3 L |
| − grain absorption | 5 L |
| − tun deadspace | 1 L |
| = Pre-boil, cold | 27.3 L |
| Pre-boil, hot in the kettle | 28.5 L |
| − boil-off | 4.5 L |
| = Post-boil, hot | 24 L |
| Post-boil, cooled | 23 L |
| − kettle loss | 2 L |
| = Into the fermenter | 21 L |
| − fermenter loss | 2 L |
| = Into bottles or keg | 19 L |
Default equipment profiles (72%, 60-minute boil, 4% shrinkage), from this page's engine. Your own ledger prints from the calculator above.
Wort at the boil is roughly 4% larger than the same wort at pitching temperature. So the 7.5 gal you see in the kettle before the boil is really 7.2 gal of room-temperature wort, and the volume "missing" from the fermenter after a perfect brew day is physics, not a leak. Every number in this ledger says whether it's hot or cold; when you calibrate your kettle markings, decide which one they mean and stick to it.
What each loss is, and how to measure it once
The defaults are sensible; yours are better. Each of these takes one measurement on one brew day, and then it's in your profile forever:
| Loss | Typical | How to measure yours |
|---|---|---|
| Grain absorption | 0.10–0.13 gal/lb · 0.8–1.1 L/kg | Water in minus wort out of the mash, divided by grain weight. Depends on your crush and how long you drain. |
| Tun deadspace | 0–0.5 gal · 0–2 L | Fill the empty tun above the false bottom, drain, measure what's left. Zero for a bag or a kettle. |
| Boil-off | 1–1.5 gal/hr · 3.5–6 L/hr | Kettle volume before and after a timed boil, both hot. Depends on kettle width and flame more than anything. |
| Shrinkage | 4% | Rarely worth measuring; it's water physics. Just be consistent about hot vs cold. |
| Kettle loss | 0.25–1 gal · 1–4 L | What's left below the valve plus the trub cone you choose not to pour, after the wort is out. |
| Fermenter loss | 0.25–0.75 gal · 1–3 L | Yeast cake and dry-hop sludge you leave behind at packaging. |
Typical ranges from Palmer and common practice; the calculator uses your profile's values, and the "save to profile" button stores what you type.
Batch sparge, fly sparge, BIAB or no-sparge?
The total is the same; what changes is how it's split. Batch and fly spargers mash at a chosen thickness and add the rest as sparge water — the calculator splits it for you at your profile's thickness. BIAB and no-sparge put all the water in at once: on the metric example that's the whole 32.3 L with the grain, a 6.5 L/kg mash needing about 35.7 L of kettle. Thinner mashes convert fine; the practical limits are the kettle and how much you can lift. If the full volume won't fit, a "dunk sparge" in a second vessel takes any split you like — set the system to batch sparge and the page will tell you the two volumes.
Switch the calculator to "I collected…" and enter what's actually in the kettle. It runs the boil, the cooling and the kettle loss forward and tells you what will reach the fermenter — so you can decide now whether to top up, boil longer, or accept a smaller batch — instead of finding out at transfer. Combined with the pre-boil gravity, it's the checkpoint that saves the day.