get FermentCalc

Brewing Water Calculator

Enter your water volume, current calcium, sulfate and chloride, a calcium target and a style profile to get weighed additions of gypsum and calcium chloride with the resulting ion levels.

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Most brewery targets sit between 50 and 150 ppm calcium for mash chemistry and yeast health; there is little benefit in pushing past about 150.

The sulfate-to-chloride ratio shapes perception more than either ion alone: sulfate sharpens bitterness, chloride rounds malt sweetness. Aim near 2:1 for pale ales and IPAs, 1:1 for balanced styles, 1:2 for malty beers.

Results

Gypsum (CaSO4·2H2O)
2.19g
plus 2.53 g of calcium chloride dihydrate
Final calcium
60 ppm
Final sulfate
61.1 ppm
Final chloride
61.1 ppm
Final SO4:Cl ratio
1 : 1

How to use the brewing water calculator

  1. Start from your water report, or reverse osmosis water at zero.
  2. Enter the treated volume for the full batch, not the mash only.
  3. Set the calcium target and pick the style profile.
  4. Weigh the salts on a 0.1 g scale and stir until fully dissolved.

Gypsum carries calcium and sulfate; calcium chloride carries calcium and chloride. The calculator solves both doses at once so the calcium lands on target while the sulfate-to-chloride ratio matches the profile you picked. Additions are computed per treated volume, so entering the whole batch spreads the salts correctly across mash and sparge water combined.

Gypsum: 23.3% Ca, 55.8% SO4; CaCl2·2H2O: 27.3% Ca, 48.3% Cl, dosed in grams per treated volume

Water chemistry and hop schedule work together: sulfate sharpens what the IBU calculator counts, and a darker grain bill changes how prominent the profile tastes - try the beer color calculator to see where the recipe sits.

Frequently asked questions

Should I treat mash water and sparge water separately?

The math works either way because salts dose per liter. Treating the combined volume is simpler and lands the same average profile; splitting lets you push the mash harder while keeping sparge water gentle. Just make sure the volume you enter matches the water the salts actually touch.

Why does the calculator ignore magnesium, sodium and bicarbonate?

Gypsum and calcium chloride are the workhorse salts for flavor-ion shaping, and the sulfate-to-chloride ratio only involves those two. Bicarbonate controls mash pH, which needs a water report with alkalinity and a different calculation; magnesium and sodium add flavor at low levels but do not help hit this ratio.

Can I use this for reverse osmosis water?

Yes - enter zeros for all current ions and it computes the full profile from scratch. RO water is the easiest starting point because nothing interferes with the target; distilled water works identically. Well water varies seasonally, so re-check the report before reusing saved numbers.