Coffee Water Recipe Calculator

Recipe mode:

Use source + RO blend for tap water that needs dilution; use RO/distilled when starting from near-zero minerals.

Target profile:

Pick the closest brew goal, then adjust the target ppm fields if your recipe calls for a different point.

Batch size:

Enter the amount of brew water you want to mix and store.

Source GH:

Measure total hardness before deciding whether to dilute or add hardness mineral.

ppm

Source KH:

Measure alkalinity separately from GH; TDS alone cannot tell you the buffer level.

ppm

Source TDS:

Use a TDS meter reading as a broad check, not as a substitute for GH and KH tests.

ppm

Target GH:

Filter recipes often start near 50-90 ppm, with method and taste deciding the final target.

ppm

Target KH:

Lower KH keeps acidity lively; higher KH buffers sharper coffees but can mute brightness.

ppm

Hardness mineral:

Choose the mineral used to raise GH when diluted or RO water is below target.

Buffer mineral:

Choose the bicarbonate used to raise KH and soften perceived acidity.

Measured pH:

pH is less useful than alkalinity for taste, but extremes still deserve a caution.

Chlorine or chloramine present

Flag this when source water has disinfectant taste, smell, or a positive test strip.

Audit for espresso machine use

Adds scale and corrosion cautions for boiler use; it is not equipment warranty advice.

Step	Amount	Ingredient	Note	Copy
{{ row.step }}	{{ row.amount }}	{{ row.ingredient }}	{{ row.note }}

Check	Reading	Status	Action	Copy
{{ row.check }}	{{ row.reading }}	{{ row.status }}	{{ row.action }}

Embed:

Customize

Include current inputs

Size

Advanced

Width

Height

Aspect ratio

Max height

Collapsible embed

Allow fullscreen

Referrer policy

Sandbox tokens

Changing coffee water is less like seasoning a cup and more like setting the solvent before extraction begins. The same beans, grind, dose, and brew time can taste sharp, hollow, muted, or heavy when the water carries a different mix of hardness, alkalinity, and dissolved salts.

Brewers usually track three readings before writing a recipe. General hardness, or GH, estimates calcium and magnesium hardness as ppm as CaCO3. Carbonate hardness, or KH, is the working alkalinity or bicarbonate-buffer reading, also expressed as ppm as CaCO3. Total dissolved solids, or TDS, is a broad meter reading for dissolved material, so it cannot identify whether the dissolved material is useful hardness, acidity buffer, disinfectant residue, sodium, chloride, or something else.

Flow from measured source water through dilution, mineral additions, and finished coffee brewing water. — A practical coffee-water recipe measures the starting water, dilutes when readings are too high, then adds only the missing hardness and buffer.

Hardness and alkalinity move the cup in different ways. Hardness affects extraction and mouthfeel, while alkalinity changes how strongly water neutralizes coffee acids. A bright washed coffee may lose clarity when alkalinity is too high, and a dark roast may taste smoother with more buffer. Espresso adds equipment risk because heated boiler water can scale, corrode, or exceed manufacturer limits even when the coffee tastes acceptable.

Coffee water reading meanings
Reading	What it tells you	Common mistake
GH	Calcium and magnesium hardness on a shared CaCO3-equivalent scale.	Assuming calcium and magnesium salts taste and scale the same way.
KH	Alkalinity, often read by brewers as the bicarbonate buffer level.	Using pH alone to judge how much acidity the water can neutralize.
TDS	A conductivity-based estimate of total dissolved material.	Treating one meter number as a complete mineral breakdown.

Water recipes also have a practical limit: minerals can raise GH and KH, but they cannot remove hardness, alkalinity, chlorine, chloramine, chloride, iron, or taints from a poor source. Test strips, drop kits, municipal reports, and TDS meters each leave gaps, so the finished batch still needs taste checks, fresh measurements when possible, and equipment guidance before it becomes a routine recipe.

How to Use This Tool:

Start with the water you can actually measure, then choose the mixing path that matches the batch you want to make.

Choose Recipe mode. Select Source water + RO/distilled blend when the source is too hard or too alkaline, RO/distilled water + minerals when the base is near zero, or Source water only, add if low when you want an audit of what source water cannot fix by itself.
Source-only mode can add missing GH or KH, but it cannot lower a source reading that already exceeds the target.
Pick Target profile, then edit Target GH and Target KH when your brew recipe calls for a different point. Manual target edits switch the profile to Custom target.
Enter Batch size in liters, milliliters, or US gallons. In blend and source-only modes, add Source GH, Source KH, and Source TDS in ppm so the dilution limit is based on the measured water.
Select the Hardness mineral and Buffer mineral. These choices change the gram amounts in Recipe Table; the GH and KH targets stay the same.
Open Advanced for pH, disinfectant, or espresso-machine review. Use Measured pH as an audit clue, and check Audit for espresso machine use before putting a recipe into boiler service.
If Chlorine or chloramine present is checked, treat the water before brewing. Minerals do not remove disinfectant taste.
Fix validation messages before relying on the recipe. Batch size must be above zero, GH/KH/TDS cannot be negative, at least one target must be above zero, and optional pH must be blank or between 0 and 14.
Read Water Recipe Snapshot first. Use Recipe Table for the mix order, Water Audit Table for cautions, Mineral Contribution Chart for source-versus-salt contribution, and GH/KH Target Map to compare source, diluted base, and final recipe.

Interpreting Results:

Start with the actual mixing amounts, then read the badge as a warning summary. Targets matched means final GH and final KH are within 2 ppm of the chosen target. Recipe needs review means at least one audit row is Low, High, or Treat first. Dilution limit reached means GH or KH remains more than 1 ppm above target because the selected mode did not dilute far enough or did not dilute at all.

Final GH and Final KH are the main recipe checks. Retest them after the salts dissolve, especially before scaling the recipe.
Estimated final TDS combines the diluted source reading with added salt mass per liter. A meter may read differently because TDS meters infer dissolved solids from conductivity.
Water Audit Table marks a reading as Low only when it is below the profile minimum and High only when it is above the profile maximum. Edge values count as in range.
Espresso machine audit is not a boiler-safety certificate. Compare the final water with the machine maker's hardness, alkalinity, TDS, chloride, and filtration guidance.

Technical Details:

Hardness and alkalinity recipes use ppm as CaCO3 because it lets different salts share one comparison scale. The finished water is not assumed to contain calcium carbonate. The number means the chosen mineral produces the same hardness or alkalinity effect as that amount of calcium-carbonate equivalent.

Dilution happens before remineralizing. When source water exceeds the target GH, target KH, or profile TDS target, the kept source fraction is constrained by the strictest ratio. RO or distilled mode uses no source contribution. Source-only mode keeps the full source contribution, so excessive GH or KH remains visible instead of being hidden by additions that cannot subtract minerals.

Formula Core:

The core calculation chooses the source fraction, fills only positive GH and KH gaps, and estimates final TDS from the diluted source plus added salt mass.

\begin{array}{lcl} L & = & batch liters after unit conversion \\ f & = & \min (1, \frac{G_{t}}{G_{s}}, \frac{K_{t}}{K_{s}}, \frac{T_{t}}{T_{s}}) \\ m_{H} & = & \max (0, G_{t} - G_{s} f) F_{H} L \\ m_{B} & = & \max (0, K_{t} - K_{s} f) F_{B} L \\ T_{final} & = & T_{s} f + \frac{(m_{H} + m_{B}) 1000}{L} \end{array}

In the formula, G is GH, K is KH, T is TDS, subscript s means source, subscript t means target, mH is hardness-mineral grams, mB is buffer-mineral grams, and F is the selected salt factor in grams per liter per ppm. A source-fraction ratio is used only when that source reading is nonzero and above its target. Milliliters are divided by 1000, and US gallons are multiplied by 3.785411784.

A 2 L blend from 120 GH, 90 KH, and 220 TDS toward a 70 GH, 40 KH, and 150 TDS target is limited by KH: 40 divided by 90 gives a source fraction near 0.444. The diluted base contributes about 53 GH and 40 KH, so only GH needs salt. With magnesium sulfate heptahydrate, the hardness addition is about 0.082 g for the 2 L batch.

Mineral factors used in coffee water recipes
Mineral	Raises	Factor, g/L/ppm	Use note
Magnesium sulfate heptahydrate / Epsom salt	GH	0.002464	Adds magnesium hardness; small doses need careful weighing.
Calcium chloride dihydrate	GH	0.001469	Adds calcium hardness; use food-safe material.
Magnesium chloride hexahydrate	GH	0.002033	Adds magnesium hardness without sulfate.
Sodium bicarbonate / baking soda	KH	0.001680	Adds bicarbonate buffer and sodium; baking powder is not a substitute.
Potassium bicarbonate	KH	0.002002	Adds bicarbonate buffer with potassium instead of sodium.

Target profiles and audit ranges for coffee water recipes
Target profile	Target GH / KH / TDS	Audit range
SCA-style filter target	70 / 40 / 150 ppm	GH 50 to 175, KH 40 to 70, TDS 75 to 250, pH 6 to 8
Bright light-roast filter	50 / 25 / 110 ppm	GH 35 to 90, KH 20 to 45, TDS 60 to 170, pH 6 to 8
Balanced daily filter	75 / 50 / 160 ppm	GH 50 to 130, KH 35 to 75, TDS 80 to 220, pH 6 to 8
High-buffer darker roast	80 / 75 / 180 ppm	GH 55 to 150, KH 55 to 100, TDS 90 to 240, pH 6 to 8
Espresso machine cautious	35 / 80 / 150 ppm	GH 20 to 80, KH 40 to 120, TDS 70 to 210, pH 6 to 8
Custom target	User GH / KH / derived TDS	GH target -20 to +50, KH target -15 to +35, pH 6 to 8

Accuracy Notes:

Water recipes are practical estimates, not laboratory certificates. Measurement error, incomplete dissolving, salt purity, scale resolution, and meter calibration can move the real batch away from the displayed number.

Use food-safe minerals and a scale that can resolve small gram or milligram amounts.
Retest GH and KH after mixing, especially before preparing a larger stored batch.
Remove chlorine or chloramine with appropriate treatment before brewing.
Compare espresso-machine water with the manufacturer guidance for that machine, not only with a taste target.

Advanced Tips:

Use Source water + RO/distilled blend when a source reading is above target; mineral salts can raise GH and KH but cannot lower them.
Keep Source GH, Source KH, and Source TDS from the same sample when comparing batches. A TDS-only update can make the dilution limit look cleaner than the real water is.
Use a larger Batch size when gram amounts fall below your scale resolution. The ppm target stays the same while the weighed dose becomes easier to measure.
Check GH/KH Target Map before changing profiles. It shows whether the source, diluted base, and final recipe move in the direction you expect.
For espresso use, treat the Espresso machine audit as an early warning and confirm chloride, iron, filtration, and warranty limits outside the recipe.

Worked Examples:

These examples use the default Epsom salt and sodium bicarbonate choices unless the case says otherwise.

Hard source water blended down

A 2 L batch using Source water + RO/distilled blend, Source GH 120 ppm, Source KH 90 ppm, Source TDS 220 ppm, and the 70 GH / 40 KH filter target keeps about 0.89 L source water and adds about 1.11 L RO/distilled water. Recipe Table then shows roughly 0.082 g Epsom salt and 0 g sodium bicarbonate.

The final estimate lands near 70 GH, 40 KH, and 139 TDS. If Water Audit Table still shows a source-water caution, that warning is about the starting water before dilution, not necessarily the finished batch.

RO water built from minerals

With RO/distilled water + minerals, a 1 L batch at 70 GH and 40 KH uses the selected salts to build the entire profile. With magnesium sulfate heptahydrate and sodium bicarbonate, Recipe Table shows about 0.172 g hardness mineral and 0.067 g buffer mineral.

Estimated final TDS is about 240 ppm because the estimate uses actual salt mass per liter. That can look higher than the profile reference while Final GH and Final KH still match the recipe target.

Source-only audit with too much alkalinity

In Source water only, add if low, a source at 60 GH and 120 KH against a 70 GH / 40 KH target can add the missing GH but cannot remove alkalinity. Water Recipe Snapshot should show Dilution limit reached, and Water Audit Table should mark Final KH as high.

The corrective path is dilution or a different source water. Adding more hardness mineral may change extraction, but it will not bring KH down to the target.

FAQ:

Can I use only a TDS meter?

No. Source TDS helps limit dilution, but the recipe needs Source GH and Source KH because two waters with the same TDS can brew and scale very differently.

Why did the result say dilution limit reached?

That status appears when the diluted base or source-only path remains more than 1 ppm above the target GH or KH. Use more RO/distilled water, pick a lower-mineral source, or choose a higher target if that is intentional.

Why does pH not drive the recipe?

The optional Measured pH field is an audit check only. KH usually tells more about how water will buffer coffee acids, while pH mainly flags extreme readings that deserve investigation.

Is the espresso-machine audit enough for boiler safety?

No. The Espresso machine audit warns about broad hardness, TDS, and buffer ranges, but it does not check every manufacturer limit such as chloride, iron, filtration type, or warranty language.

Why are my gram amounts so small?

GH and KH targets are ppm-level changes, so 1 L and 2 L batches often need tenths or hundredths of a gram. Use a precise scale, or mix a larger batch so the measured salt amounts are easier to weigh.

Glossary:

GH: General hardness from calcium and magnesium, expressed here as ppm as CaCO3.
KH: The working alkalinity or bicarbonate-buffer reading, expressed here as ppm as CaCO3.
TDS: Total dissolved solids, a broad concentration estimate that does not identify which minerals are present.
RO water: Reverse-osmosis water, used as a low-mineral base for dilution or remineralizing.
Buffer: Alkalinity that resists pH change and can reduce perceived acidity in brewed coffee.
Scale: Mineral deposit, often calcium or magnesium carbonate, that can form when heated water chemistry favors precipitation.

References:

The SCAE Water Chart, Speciality Coffee Association of Europe.
Water and Coffee Acidity: How to Adapt Your Water for Different Extraction Methods, Specialty Coffee Association.
Addressing Water Quality Issues: The TDS Meter, Specialty Coffee Association.
La Marzocco Water Specification, La Marzocco.