Brewing Water Chemistry Calculator
Calculate mineral additions for your brewing water.
Adjust calcium, magnesium, sulfate, and chloride levels to hit your target water profile for any beer style.
Why water matters in beer
The mash and the boil are essentially a chemistry lab where dissolved minerals shape pH, enzyme activity, hop bitterness perception, and the malt-vs-hop balance of the finished beer. Two breweries using the same recipe with different water can produce noticeably different beers. The IPA-friendly water of Burton-on-Trent and the soft Pilsner water of Plzeň are textbook examples of how source water shaped entire beer styles.
The four ions that matter most
| Ion | Useful range (ppm) | What it does |
|---|---|---|
| Calcium (Ca²⁺) | 50 to 150 | Drops mash pH, helps yeast flocculate, protects mash enzymes |
| Magnesium (Mg²⁺) | 5 to 30 | Yeast nutrient; over 50 ppm tastes metallic |
| Sulfate (SO₄²⁻) | 50 to 350 | Sharpens hop bitterness, drier finish |
| Chloride (Cl⁻) | 30 to 200 | Rounds malt character, fuller mouthfeel |
The sulfate-to-chloride ratio is the single most discussed water number in homebrewing. Higher SO₄ (Burton style, 2:1 to 4:1) accentuates hops; higher Cl (London or Munich style, 1:2) accentuates malt.
The math for additions
Gypsum (calcium sulfate, CaSO₄·2H₂O): 1 g per litre adds about 61.5 ppm Ca²⁺ and 147.4 ppm SO₄²⁻.
Calcium chloride (CaCl₂·2H₂O): 1 g per litre adds about 272 ppm Ca²⁺ and 482 ppm Cl⁻.
To add 50 ppm calcium across a 20 L batch with gypsum:
grams_needed = (50 ÷ 61.5) × 20 = 16.3 g
That gypsum addition also bumps sulfate by 50 × (147.4 ÷ 61.5) = 120 ppm. You cannot raise calcium with these salts without bringing sulfate or chloride along for the ride.
Style-typical water profiles
| Style | Ca | SO₄ | Cl | SO₄ : Cl |
|---|---|---|---|---|
| Pilsner | 50 | 50 | 50 | 1 : 1 |
| English bitter | 100 | 150 | 100 | 1.5 : 1 |
| IPA / pale ale | 100 | 250 | 75 | 3.3 : 1 |
| Stout / porter | 100 | 75 | 150 | 1 : 2 |
| Munich helles | 75 | 50 | 75 | 1 : 1.5 |
Start with reverse osmosis if you can
If your tap water is hard, full of chloramine, or wildly variable by season, the cleanest path is to start with RO water (cheap from a supermarket vending machine, or run a small under-sink RO membrane at home) and build your profile from zero. You only need to know the four minerals you added, not whatever your municipal water department put in this month or next.