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Brewing water chemistry calculator

Start from your water report (or zeros for RO and distilled water), add salts in grams, and see the resulting calcium, magnesium, sodium, sulfate, chloride and bicarbonate, the sulfate-to-chloride ratio and residual alkalinity.

A digital gram scale with a stainless weighing pan
Photo: Stan Zurek, CC BY-SA 3.0, via Wikimedia Commons
Units
Your source water, ppm (water report; 0 for RO or distilled)
Salt additions, grams (grams in both unit systems)
SO4 : Cl ratio—
Residual alkalinity (as CaCO3)—
Alkalinity (as CaCO3)—
Campden tablets for chloramine—

No mash pH prediction here: that needs a grain acidity model (Bru’n Water, Brewfather) and a calibrated pH meter.

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Chemicals: label directions onlyUse sanitizers, cleaners, acids and salts only at the dilution and contact time on the label. Wear eye protection with acids and powders, add acid to water, keep them away from children and food prep. Star San is EPA-registered (Reg. No. 65001-1) as a no-rinse sanitizer at label dilution.Source: EPA Star San label

How it’s calculated

  1. Ion ppm added = grams ÷ gallons × ppm per g/gal (table)
  2. Alkalinity as CaCO3 = HCO3 × 50/61
  3. Residual alkalinity: RA = Alkalinity − (Ca / 3.5 + Mg / 7)
  4. SO4:Cl ratio = sulfate ppm ÷ chloride ppm

Assumptions

  • No mash pH prediction: that needs a grain acidity model (Bru'n Water, Brewfather) and a pH meter.
  • Chalk dissolves poorly in plain water; its numbers assume full solubility.
  • Use non-iodized salt only, and food-grade brewing salts per the label.

Worked example: 5 g gypsum + 2 g calcium chloride in 5 gal of RO water → Ca 90, SO4 147, Cl 51 ppm; SO4:Cl about 2.9.

Sources: Palmer & Kaminski, Water: A Comprehensive Guide for Brewers; BYO: brew-water spreadsheet; Craft Beer & Brewing: water chemistry tool

For guidance only: verify with your own readings, your equipment’s manual and the product labels.

The salt table behind the numbers

What 1 gram of each salt adds to 1 US gallon (ppm)

SaltCaMgNaSO4ClHCO3
Gypsum CaSO4·2H2O61.5——147.4——
Calcium chloride CaCl2·2H2O72———127.4—
Epsom salt MgSO4·7H2O—26.1—103——
Baking soda NaHCO3——72.3——191.9
Table salt (non-iodized) NaCl——103.9—160.3—
Chalk CaCO3
Poorly soluble in plain water; real additions dissolve only partly		105.8————CO3 158.4

RA = Alkalinity − (Ca / 3.5 + Mg / 7) (all ppm; alkalinity as CaCO3 = HCO3 × 50/61). One Campden tablet treats about 20 gal (75 L) of chloraminated water (AHA/BYO guidance; check your tablet's label). Sources: Palmer & Kaminski, Water: A Comprehensive Guide for Brewers (Brewers Publications); BYO: Charts & calculators (brew-water spreadsheet); Craft Beer & Brewing: Brewing tools (water chemistry). Gypsum and calcium chloride are checked against published calculators; the rest are stoichiometric values.

What this calculator won't do

It does not predict mash pH. That depends on the acidity of your grain bill, which needs a model such as Bru'n Water or Brewfather and a calibrated pH meter to check. Use brewing salts only as their labels direct.

Questions

How much gypsum for an IPA?
It depends on your water and taste. Many hoppy recipes push sulfate well above chloride; use the calculator to see the ppm your additions give, and change one thing per batch.
How do I remove chloramine?
Campden tablets: about one per 20 gallons, per AHA and BYO guidance. Check your tablet's label.

Sources

  1. Palmer & Kaminski, Water (Brewers Publications)