Mash Water Planner

It plans every drop of water on your brew day in one place: strike water volume and temperature, sparge water volume (batch sparge or no-sparge), a BIAB full-volume mode, a “can you mash it” mash-tun capacity check, a kettle volume planner, a boil-off calibrator that learns your system, and a recipe-scaling tab. You enter batch size, grain bill and equipment losses; it returns one unified water balance — total water needed, strike vs sparge split, first and second runnings, and pre-boil volume — in metric or imperial units. Everything runs 100% in your browser; no data ever leaves your device.

Whether you call it a strike water volume calculator or a mash strike water calculator, the math is the same: strike water volume = grain weight x mash thickness. Mash thickness is usually 1.0 to 2.0 quarts per pound of grain, with 1.25 qt/lb the classic default (John Palmer, How to Brew). So 12 lb of grain at 1.25 qt/lb needs 3.75 gallons of strike water — that is exactly how much water to mash with. Thinner mashes (1.5-2.0) are easier to stir and suit highly modified malts; thicker mashes (1.0) are used when tun space is tight. The Water Balance tab above computes this automatically and clamps strike to your total water if the ratio would over-fill.

The standard formula from Palmer's How to Brew is: strike temp = target mash temp + (0.2 / ratio) x (target mash temp - grain temp), with ratio in quarts per pound. For 10 lb of grain at 68F, targeting 152F at 1.25 qt/lb: 152 + (0.2/1.25) x 84 = about 165.5F. The tool uses the more general heat-balance form, which adds your mash tun's thermal mass (a cold cooler steals heat — a plastic cooler behaves like roughly 3.5 lb of extra cold water). Pick a tun preset or enter a custom value, or preheat your tun to skip the correction entirely. In short, this strike water temp calculator answers both the temperature and the volume in one step.

If you searched for how to calculate sparge water volume or how much sparge water to use, the formula is simple: sparge water = total water needed - strike water. Work backwards from your batch: total water = pre-boil volume + grain absorption, and pre-boil volume = (batch size + trub/kettle loss) / 0.96 + boil-off. For a 5-gallon batch with 12 lb of grain, 1 gal/hr boil-off over 1 hour and 0.5 gal trub loss: total water is about 8.23 gal, strike at 1.25 qt/lb is 3.75 gal, so sparge is about 4.48 gal. The planner shows this full chain — flameout volume, pre-boil, total, strike and sparge — so you can see exactly where each gallon goes.

Sparge at 168-170F (75-77C) — this sparge water temp range is the safe zone. So does sparge water temp matter? Yes: the goal is to stop enzymatic conversion and improve wort flow without extracting tannins. Below 168F is safe but may run off slowly; above 170F the risk of harsh, astringent tannins rises, especially if mash pH is above 6. That is the honest limit of this tool: it plans volumes and temperatures, but water chemistry and mash pH are a separate discipline — this planner deliberately does not model pH or salt additions.

A brew in a bag water calculator has one job: total water = pre-boil volume + (grain weight x absorption). BIAB uses full-volume mashing: all the water goes in at once, no sparge. BIAB absorption is lower because you squeeze the bag — about 0.075 gal/lb vs 0.125 gal/lb for traditional mashing. So how much water for BIAB? For a 5-gallon batch with 12 lb of grain, 1 gal/hr boil-off and 0.5 gal trub loss, BIAB needs about 7.63 gal total in the kettle. The BIAB tab computes this, and its built-in biab strike water calculator gives the infusion temperature at full volume — because the mash is very thin (often 2.5+ qt/lb), expect strike temps only ~6-7F above your mash target.

This mash tun capacity calculator — also called a mash tun volume calculator or mash tun size calculator — uses one rule: mash volume = strike water volume + (grain weight x 0.08 gal/lb), because a pound of grain displaces roughly 0.32 quarts. A 12-lb grain bill at 1.25 qt/lb occupies about 4.71 gallons, which fits a 5-gallon cooler with 0.29 gal of headroom. If it does not fit, the tool recommends a minimum tun size (mash volume / 0.85, keeping safe headroom) and the note under the capacity check lists fixes: thicker mash, split the batch, skip the sparge, or go BIAB.

The average boil off rate for homebrewing is 0.5 to 1.5 gallons per hour, depending on kettle diameter, burner power and boil vigor — wider kettles boil off more. Do not trust a generic number: the Boil-off Calibrator tab learns yours. The boil off rate formula is (pre-boil volume - post-boil volume) / time — a wort boil off calculator in one line. Fill to a measured pre-boil volume, boil for a timed 30-60 minutes, measure the post-boil volume, and it computes your rate. Example: 7.0 to 6.2 gallons in one hour = 0.8 gal/hr. Measure once, reuse forever — unless you change kettle or burner.

Three things eat volume between kettle and fermenter. First, grain absorption (~0.125 gal/lb stays in the spent grain). Second, boil-off (your measured gal/hr x boil time). Third, hot wort shrinks about 4% as it cools to fermentation temperature, plus trub and kettle deadspace left behind. A 5-gallon batch with 12 lb of grain typically needs about 8.2 gallons of total water and a 6.7-gallon pre-boil. The planner shows each stage so the “missing” volume is accounted for.

Scale grain, water and volumes by the ratio of batch sizes — the Scaling tab does this, whether you are scaling up beer recipes or planning to scale down a beer recipe. But two things do not scale linearly, and the tool is honest about them. First, boil-off rate is a property of your kettle and burner, not your batch: doubling a 5-gallon recipe to 10 gallons doubles the grain and water but keeps boil-off at the same gallons-per-hour. Second, hop bitterness does not scale linearly because utilization depends on wort gravity — rescale hops by volume ratio as a starting point, then verify IBUs separately. Water, grain and volumes: linear. Boil-off and hops: not.

You have five levers, roughly in this order: (1) thicken the mash to 1.0 qt/lb — less strike water, same grain; (2) skip the sparge (no-sparge mashing uses less total tun space at the cost of efficiency); (3) split into two smaller mashes; (4) get a bigger tun (the tool recommends a size); (5) switch to BIAB, where the kettle is the tun. Never overfill past ~90% of tun capacity — dough balls and stuck sparges live there.

Batch sparge splits the total water into a strike infusion and one or two sparge runnings — typically the best efficiency for the equipment. As a batch sparge water calculator, this planner shows first runnings (strike minus absorption) and second runnings separately. No-sparge puts all the water in the mash (like BIAB but in a tun): strike volume = total water, sparge = 0, which simplifies the day but costs roughly 5-10% efficiency. The planner handles both: set your mash thickness and it clamps automatically.

No, deliberately. Water chemistry (calcium, sulfate/chloride ratio, mash pH prediction) is a separate, chemistry-heavy discipline with tools like Bru'n Water and the water-chemistry calculators — this planner covers volumes, temperatures, capacities and scaling only. It also does not model sparge pH: the FAQ on sparge temperature notes the 170F tannin guardrail, which is the volume-planning-relevant part.

Homebrewing laws vary widely by country and by state/province — in some places it is fully legal, in others it requires a license or is prohibited, and minimum drinking ages differ everywhere. Check your local regulations before brewing, and only use this tool if you are of legal drinking age where you live. The tool itself is a planning calculator: it gives estimates, not professional advice. On brew day, treat strike water with respect — 165F+ water scalds — and always verify final gravity is stable before bottling to avoid over-carbonated bottles.

Yes. Toggle between Imperial (gallons, pounds, Fahrenheit) and Metric (liters, kilograms, Celsius) at the top of the tool — a strike water calculator in metric works exactly the same — all math is identical, only the display converts. Mash thickness is entered as L/kg in metric mode (1.25 qt/lb = about 2.6 L/kg). Boil-off shows in L/hr, grain absorption in L/kg. If you learned brewing from US sources, the imperial defaults will match your recipes; European and Australian brewers can work entirely in metric.

Yes and yes. It is free with no account, no sign-up and no limits, and it runs 100% in your browser — every calculation happens on your device, nothing is sent to any server, and it works offline after the page loads. Unlike some brewing calculators that require accounts to save recipes, this one has nothing to save and nothing to track.