Coffee Calculators

Water chemistry

Barista Water Recipe Calculator

GH/KH is the short version of brewing water: general hardness (calcium and magnesium) and carbonate hardness (alkalinity). Specialty recipes often sit near 50–80 ppm GH and ~40 ppm KH as CaCO₃. This page doses Epsom salt for GH and baking soda for KH into a known volume of very soft or distilled water.

Inputs

Units
ppm

ppm as CaCO₃. Magnesium from Epsom in this recipe.

ppm

Alkalinity as ppm CaCO₃ from sodium bicarbonate.

L

Litres of distilled or RO water you will fortify.

Results

Epsom salt
197.0mg
Baking soda
67.2mg
Epsom salt
0.197g
Baking soda
0.067g

The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.

Example products

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Calculation method

Epsom salt (MgSO₄·7H₂O) contributes GH: milligrams ≈ target GH ppm × litres × 2.46. Baking soda contributes KH: milligrams ≈ target KH ppm × litres × 1.68. Grams are those milligrams divided by 1000. The factors assume heptahydrate Epsom and sodium bicarbonate into mineral-free water. Calcium chloride recipes need a third salt this page does not dose.

Exact formula

epsomMg ≈ targetGhPpm × volumeL × 2.46. bakingSodaMg ≈ targetKhPpm × volumeL × 1.68. Grams are mg / 1000. Limits: Hydrate form, tap minerals already present, and potassium bicarbonate alternatives omitted; KH from bicarb is not a full SCA ion recipe.

Concentrate bottles

With a 0.1 g scale, weigh the salts for 10 L instead (about 0.67 g of baking soda for 40 ppm KH), dissolve them in 100 ml of distilled water and add 10 ml per litre. The weighing error shrinks tenfold. Keep GH and KH in separate, labelled bottles so you do not fortify twice.

Espresso vs filter

Espresso often likes a bit more GH for sweetness; filter can taste sharper at the same KH. Change one target at a time and pull the same coffee.

Frequently asked questions

Can I use tap water as the base?

Only if you know its GH and KH and subtract them. This calculator starts from zero. Adding 40 ppm KH on top of 120 ppm tap KH mutes every espresso.

Why no calcium?

This is the simple magnesium + bicarb pair. Many barista recipes also add CaCl₂. If you do, lower the Epsom dose: calcium adds GH that these outputs do not count.

Scale in the kettle?

Carbonate scale needs both: hardness ions from GH and carbonate from KH. Heating can drop out the carbonate hardness, roughly the smaller of the two; magnesium scale forms more slowly than calcium scale, but it still forms. Descale on hardness and throughput, not because the recipe ‘is soft’.

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