hobby calculator

Home Brewing Water Chemistry Calculator

Turn source water, RO dilution and salt additions into a full ion profile, sulfate-chloride ratio and residual alkalinity.

Each salt contributes ions in proportion to its formula weight: gypsum gives 232.8 ppm calcium and 558.0 ppm sulfate per gram per litre, calcium chloride 272.6 and 482.3 chloride. Two derived numbers decide the beer — the sulfate to chloride ratio, where below 0.8 reads malty and above 1.5 accentuates bitterness, and Kolbach residual alkalinity, which is alkalinity as CaCO3 minus calcium over 3.5 minus magnesium over 7.

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Batch VolumeL

Diluted With RO/Distilled%

Source Calciumppm

Source Magnesiumppm

Source Sodiumppm

Source Sulfateppm

Source Chlorideppm

Source Bicarbonateppm

Gypsumg

Calcium Chlorideg

Epsom Saltg

Table Saltg

Baking Sodag

Chalkg

Results

Sulfate : Chloride Ratio

3.86 : 1

BalanceHop-forward — dry and accentuated

Calcium91.3 ppm

Magnesium3.0 ppm

Sodium7.0 ppm

Sulfate162.8 ppm

Chloride42.2 ppm

Bicarbonate32.5 ppm

Alkalinity as CaCO₃26.6 ppm

Residual Alkalinity0.1

Grist SuitabilityModerate — suits amber and lightly roasted grists

Total Hardness as CaCO₃240.2 ppm

Calcium in the 50–150 ppm RangeYes

Sodium Above 150 ppmNo

Sulfate Above 350 ppmNo

Total Salt Added10.0 g (0.333 g/L)

Added by the SaltsCa 80.3, SO₄ 148.8, Cl 32.2

Tip

Worth keeping open on brew day: water adjustments are the cheapest change in brewing and the one most likely to move a beer from decent to good.

Formula

Brewing salt contributions and water chemistry

Ion contribution (ppm) = grams / litres x contribution per g/L

  Gypsum  CaSO4.2H2O     Ca 232.8   SO4 558.0
  CaCl2.2H2O             Ca 272.6   Cl  482.3
  Epsom   MgSO4.7H2O     Mg  98.6   SO4 389.7
  Salt    NaCl           Na 393.4   Cl  606.6
  Soda    NaHCO3         Na 273.7   HCO3 726.3
  Chalk   CaCO3          Ca 400.4   HCO3 1219.2

Diluted source ion = source ppm x (1 - RO share)
Final ion = diluted source + salt contribution

Alkalinity as CaCO3 = HCO3 x 50 / 61.016
Residual Alkalinity = Alkalinity as CaCO3 - Ca/3.5 - Mg/7

Each salt contributes ions in fixed proportion to its formula weight, so the additions are chemistry rather than guesswork: gypsum is 40.078/172.17 of its mass as calcium, which is 232.8 mg per gram. The two derived numbers matter most. The sulfate-to-chloride ratio sets whether the finish reads dry and bitter or soft and malty. Residual alkalinity, Kolbach's measure, says how strongly the water resists the acidity of the malt — pale grists want it near zero, dark roasted grists want it high.

Step by step

How the calculation works

1Enter your water report, the share you are cutting with reverse osmosis or distilled water, and the salt additions in grams for the batch volume shown. Dilution is applied to the source ions first, then the salts are added on top.
2Target calcium between 50 and 150 ppm. Below 50 the mash enzymes, protein coagulation and yeast flocculation all suffer; above 150 there is no further benefit and the water starts tasting mineral.
3The sulfate-to-chloride ratio is the flavour lever. Around 3 or 4 to 1 gives a dry, hop-accentuated West Coast finish; around 1 to 3 gives the soft, rounded mouthfeel a hazy is built on. Keep sulfate under about 350 ppm and sodium under about 150.
4Residual alkalinity has to match the grist. Pale beers want it near or below zero; stouts and porters want it high, because dark roasted malts are strongly acidic and need carbonate to push against. Getting this wrong is the most common water mistake in brewing.
5Chalk is modelled at full dissolution and will not achieve that in a real mash — use baking soda or pickling lime when alkalinity is genuinely needed. Once the water is set, the [homebrew ABV and priming calculator](/calculators/homebrew-abv-priming-calculator) covers the other end of the brew day.

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Home Brewing Water Chemistry Calculator

Turn source water, RO dilution and salt additions into a full ion profile, sulfate-chloride ratio and residual alkalinity.

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Batch VolumeL

Diluted With RO/Distilled%

Source Calciumppm

Source Magnesiumppm

Source Sodiumppm

Source Sulfateppm

Source Chlorideppm

Source Bicarbonateppm

Gypsumg

Calcium Chlorideg

Epsom Saltg

Table Saltg

Baking Sodag

Chalkg

Results

Sulfate : Chloride Ratio

3.86 : 1

BalanceHop-forward — dry and accentuated

Calcium91.3 ppm

Magnesium3.0 ppm

Sodium7.0 ppm

Sulfate162.8 ppm

Chloride42.2 ppm

Bicarbonate32.5 ppm

Alkalinity as CaCO₃26.6 ppm

Residual Alkalinity0.1

Grist SuitabilityModerate — suits amber and lightly roasted grists

Total Hardness as CaCO₃240.2 ppm

Calcium in the 50–150 ppm RangeYes

Sodium Above 150 ppmNo

Sulfate Above 350 ppmNo

Total Salt Added10.0 g (0.333 g/L)

Added by the SaltsCa 80.3, SO₄ 148.8, Cl 32.2

Tip

Worth keeping open on brew day: water adjustments are the cheapest change in brewing and the one most likely to move a beer from decent to good.

Summary

Key output metrics

Sulfate : Chloride

3.86 : 1

Hop-forward — dry and accentuated

Residual Alkalinity

0.1

Moderate — suits amber and lightly roasted grists

Calcium

91.3 ppm

Inside the usual 50 to 150 ppm range

D3 visualization

Finished Water Profile

The ion profile after dilution and salt additions, in parts per million. Sulfate and chloride are the flavour pair; calcium supports the mash and the fermentation; bicarbonate sets the alkalinity.

Guide

How to understand and use this calculator

Quick Answer — How Brewing Salts Change Your Water

Each brewing salt contributes ions in proportion to its formula weight. One gram of a salt dissolved in one litre of water contributes, in parts per million, the ion's share of the salt's molar mass multiplied by 1,000. Those figures are fixed chemistry, not a matter of opinion:

Gypsum (CaSO₄·2H₂O) — 232.8 ppm calcium, 558.0 ppm sulfate per g/L
Calcium chloride (CaCl₂·2H₂O) — 272.6 ppm calcium, 482.3 ppm chloride
Epsom salt (MgSO₄·7H₂O) — 98.6 ppm magnesium, 389.7 ppm sulfate
Table salt (NaCl) — 393.4 ppm sodium, 606.6 ppm chloride
Baking soda (NaHCO₃) — 273.7 ppm sodium, 726.3 ppm bicarbonate
Chalk (CaCO₃) — 400.4 ppm calcium, 1,219.2 ppm bicarbonate

Two numbers matter more than the individual ions. The sulfate-to-chloride ratio sets how the finish reads: below about 0.8 the beer reads soft and malty, 0.8 to 1.5 is balanced, and above 1.5 the bitterness is accentuated and the finish turns dry. And residual alkalinity decides whether the mash pH lands where the grist wants it.

How to Use This Calculator: A West Coast IPA

Enter your source water report, the percentage you are cutting with reverse osmosis or distilled water, and the salt additions in grams for the full batch volume.

Take a 30-litre batch built on moderately soft tap water — 22 ppm calcium, 6 magnesium, 14 sodium, 28 sulfate, 20 chloride, 65 bicarbonate — cut 50% with RO, then treated with 8 g gypsum and 2 g calcium chloride.

The dilution halves every source ion first: calcium falls to 11, sulfate to 14, chloride to 10, bicarbonate to 32.5. Then the salts add 80.3 ppm calcium, 148.8 ppm sulfate and 32.2 ppm chloride across 30 litres.

The finished profile is 91.3 calcium, 3.0 magnesium, 7.0 sodium, 162.8 sulfate, 42.2 chloride, 32.5 bicarbonate. The sulfate-to-chloride ratio is 3.86 to 1 — firmly hop-forward, dry and accentuated, which is exactly the West Coast character. Calcium at 91 ppm sits comfortably inside the 50 to 150 range brewers target, and sulfate at 163 is assertive without approaching the 350 ppm point where it starts tasting harsh and mineral.

Residual alkalinity comes out at 0.1, essentially neutral, which suits a pale grist that has little acidity of its own to fight. Once the water is set, the homebrew ABV and priming calculator handles the other end of the same brew day.

A Second Example: A Hazy IPA and a Stout, Both From RO

Building from 100% RO water is the cleanest approach because there is nothing to subtract — you are constructing the profile rather than correcting one.

For a 23-litre hazy IPA, 1.5 g gypsum and 5.5 g calcium chloride produce 80.4 calcium, 36.4 sulfate, 115.3 chloride and a sulfate-to-chloride ratio of 0.32 — malt-forward, soft and rounded, which is the mouthfeel a hazy is built around. Residual alkalinity is −23.0, appropriately low for a pale grist, and calcium sits in range at 80 ppm.

The identical batch size for a stout takes a different shape: 2 g gypsum, 2 g calcium chloride and 4 g baking soda give 43.9 calcium, 47.6 sodium, 48.5 sulfate, 41.9 chloride, 126.3 bicarbonate. The ratio is 1.16 — balanced — but the important number is the residual alkalinity of 91.0, which is high and suits brown and porter grists. That alkalinity is deliberate: dark roasted malts are strongly acidic, and without carbonate to push against them the mash pH drops too far and the beer turns thin and sour rather than round.

Note the calcium in that stout is 43.9 ppm, just below the usual 50 ppm floor. That is a real trade-off rather than an error — adding more calcium would drag the residual alkalinity back down, which is the opposite of what the grist needs. Brewing water is a system of competing targets, not a checklist, and the calculator shows all of them at once so the trade-off is visible rather than hidden.

Reading the Numbers That Matter

Calcium (50 to 150 ppm) is the workhorse. It supports enzyme activity in the mash, helps yeast flocculate, aids protein coagulation in the boil, and drops mash pH by reacting with malt phosphates. Below 50 ppm the mash and the fermentation both suffer; above 150 there is no further benefit and the water starts tasting mineral.

Sulfate and chloride are the flavour pair. Sulfate accentuates hop bitterness and dries the finish; chloride enhances malt sweetness and fullness. It is the ratio between them, not the absolute levels, that shapes perception — though sulfate above about 350 ppm turns harsh and chloride above roughly 200 ppm can read as flabby.

Sodium (under about 150 ppm) rounds and sweetens in small amounts and tastes salty above that. It usually arrives as a by-product of baking soda rather than as a deliberate addition.

Residual alkalinity is the Kolbach figure: alkalinity as calcium carbonate minus calcium over 3.5 minus magnesium over 7. It measures how much the water resists the acidity of the malt. Pale grists want it near or below zero; dark roasted grists want it high, because they bring their own acid. Getting this wrong is the single most common water mistake, and it shows up as a mash pH outside the 5.2 to 5.6 range where conversion and flavour both work best.

One warning: chalk barely dissolves in water. The figures here assume full dissolution, which does not happen in a mash without dissolved CO2 to help it. Most brewers use pickling lime or baking soda instead when alkalinity is genuinely needed. Treat any result relying on chalk as an upper bound on what you will actually get.

Limitations

This calculates the ion profile of the finished water. It does not predict mash pH, and the two are not the same thing. Mash pH depends on the grist — how much of it is base malt, crystal, roasted or acidulated — as much as on the water, and predicting it requires a full mash model with malt buffering data. Residual alkalinity tells you which direction the water pushes; only a pH meter tells you where the mash actually landed.

Chalk is modelled at 100% dissolution and will not achieve that in practice. Pickling lime and baking soda are the practical alternatives when alkalinity is needed, and both are handled here.

The salt additions are applied to the whole batch volume as a single figure. Many brewers split additions between the mash and the sparge, or treat only the mash water, and the effective concentration in each is then different from the batch-average figure shown. If you are splitting, run the mash volume and the sparge volume as separate calculations.

Finally, a water report is a snapshot. Municipal supplies vary seasonally, sometimes substantially, and utilities blend sources through the year. If your source water is entering a recipe you care about, either request a recent report, test it yourself, or do what most brewers eventually do and build from reverse osmosis, where the starting point is zero and nothing changes between batches. That predictability is worth more than the specific profile.

Related Calculators

The Homebrew ABV Priming Sugar Calculator covers the other end of the same brew day, from original and final gravity through to the priming sugar for a target carbonation. The Coffee-to-Water Brew Ratio Calculator applies a similar ratio-driven approach to the other drink where water chemistry quietly decides the result. And the Baker's Percentage Calculator uses the same proportional thinking for the other craft where a few grams either way changes the result.

Related concepts

Sulfate-to-Chloride Ratio

The balance between the two flavour ions. Sulfate accentuates hop bitterness and dries the finish; chloride enhances malt fullness. The ratio between them shapes perception more than either level alone.

Residual Alkalinity

Kolbach's measure of how strongly water resists the acidity of malt: alkalinity as CaCO3 minus calcium over 3.5 minus magnesium over 7. It is what matches a water profile to a grist.

Brewing Salts

Gypsum, calcium chloride, Epsom salt, table salt, baking soda and chalk. Each contributes fixed proportions of specific ions determined by its formula weight, which is why the additions can be calculated rather than guessed.

Frequently Asked Questions

What does gypsum do in brewing water?+

It adds calcium and sulfate — 232.8 ppm and 558.0 ppm respectively per gram per litre. Calcium supports mash enzymes and yeast flocculation; sulfate accentuates hop bitterness and dries the finish. It is the standard addition for pale, hoppy beers.

What is a good sulfate to chloride ratio?+

It depends on the beer. Below about 0.8 reads soft and malty, 0.8 to 1.5 is balanced, and above 1.5 accentuates bitterness. A West Coast IPA at 3.86 is firmly hop-forward; a hazy at 0.32 is deliberately soft and rounded.

How much calcium should brewing water have?+

Between 50 and 150 ppm for most beers. Below 50 the mash enzymes, protein coagulation and yeast flocculation all suffer; above 150 there is no further benefit and the water begins to taste mineral.

What is residual alkalinity?+

The Kolbach figure: alkalinity as calcium carbonate, minus calcium divided by 3.5, minus magnesium divided by 7. It measures how strongly the water resists the acidity of the malt. Pale grists want it near or below zero; dark roasted grists want it high, because they bring their own acid.

Should I build my brewing water from RO?+

It is the most predictable approach, because the starting point is zero and nothing varies between batches. Municipal water changes seasonally as utilities blend sources, and that variability is usually a bigger problem than any particular profile. Building from RO removes it entirely.

Why does chalk not work well?+

Because calcium carbonate barely dissolves in water without dissolved CO2 to help it. This calculator assumes full dissolution, which will not happen in a mash, so treat any chalk-based result as an upper bound. Pickling lime or baking soda are the practical alternatives when alkalinity is genuinely needed.

Does this predict my mash pH?+

No, and the two are different questions. Mash pH depends on the grist composition — base malt, crystal, roasted, acidulated — as much as on the water. Residual alkalinity tells you which direction the water pushes; a pH meter tells you where the mash actually landed.

Should I add salts to the mash or the whole batch?+

Either works, but the concentrations differ. This calculator applies additions across the batch volume you enter, so if you are treating mash and sparge water separately, run each volume as its own calculation rather than splitting the batch figure by eye.

Formula

Brewing salt contributions and water chemistry

Ion contribution (ppm) = grams / litres x contribution per g/L

  Gypsum  CaSO4.2H2O     Ca 232.8   SO4 558.0
  CaCl2.2H2O             Ca 272.6   Cl  482.3
  Epsom   MgSO4.7H2O     Mg  98.6   SO4 389.7
  Salt    NaCl           Na 393.4   Cl  606.6
  Soda    NaHCO3         Na 273.7   HCO3 726.3
  Chalk   CaCO3          Ca 400.4   HCO3 1219.2

Diluted source ion = source ppm x (1 - RO share)
Final ion = diluted source + salt contribution

Alkalinity as CaCO3 = HCO3 x 50 / 61.016
Residual Alkalinity = Alkalinity as CaCO3 - Ca/3.5 - Mg/7

Step by step

How the calculation works

1Enter your water report, the share you are cutting with reverse osmosis or distilled water, and the salt additions in grams for the batch volume shown. Dilution is applied to the source ions first, then the salts are added on top.
2Target calcium between 50 and 150 ppm. Below 50 the mash enzymes, protein coagulation and yeast flocculation all suffer; above 150 there is no further benefit and the water starts tasting mineral.
3The sulfate-to-chloride ratio is the flavour lever. Around 3 or 4 to 1 gives a dry, hop-accentuated West Coast finish; around 1 to 3 gives the soft, rounded mouthfeel a hazy is built on. Keep sulfate under about 350 ppm and sodium under about 150.
4Residual alkalinity has to match the grist. Pale beers want it near or below zero; stouts and porters want it high, because dark roasted malts are strongly acidic and need carbonate to push against. Getting this wrong is the most common water mistake in brewing.
5Chalk is modelled at full dissolution and will not achieve that in a real mash — use baking soda or pickling lime when alkalinity is genuinely needed. Once the water is set, the [homebrew ABV and priming calculator](/calculators/homebrew-abv-priming-calculator) covers the other end of the brew day.

Related guides

Learn more about this calculation

Guide

Home Brewing Water Chemistry Calculator

Inputs

Results

Brewing salt contributions and water chemistry

How the calculation works

Learn more about this calculation

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Understanding Calculator Formulas: How DTC Turns Inputs into Results

Homebrew ABV & Priming Sugar Calculator

Coffee-to-Water Brew Ratio Calculator

Baker's Percentage Calculator

Recipe Scaler Calculator

Key facts

Home Brewing Water Chemistry Calculator

Inputs

Results

Key output metrics

Finished Water Profile

How to understand and use this calculator

Quick Answer — How Brewing Salts Change Your Water

How to Use This Calculator: A West Coast IPA

A Second Example: A Hazy IPA and a Stout, Both From RO

Reading the Numbers That Matter

Limitations

Related Calculators

Related concepts

Frequently Asked Questions

Brewing salt contributions and water chemistry

How the calculation works

Learn more about this calculation

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Understanding Calculator Formulas: How DTC Turns Inputs into Results

Homebrew ABV & Priming Sugar Calculator

Coffee-to-Water Brew Ratio Calculator

Baker's Percentage Calculator

Recipe Scaler Calculator

Key facts

Key output metrics

Finished Water Profile

How to understand and use this calculator

Quick Answer — How Brewing Salts Change Your Water

How to Use This Calculator: A West Coast IPA

A Second Example: A Hazy IPA and a Stout, Both From RO

Reading the Numbers That Matter

Limitations

Related Calculators

Related concepts

Frequently Asked Questions