Convert any aquarium water parameter — ppm to dGH / dKH, °C / °F and meq/L — with safe-range presets for common freshwater and marine species.
| Unit | Value | Typical use |
|---|
1 dGH = 17.86 ppm CaCO₃ = 0.357 meq/L. Same conversion applies to dKH (carbonate hardness) because both are reported as calcium-carbonate equivalent. ppm and mg/L are interchangeable for dilute aquarium water.
Temperature: °C = (°F − 32) × 5/9. Most freshwater tropicals sit at 24–27 °C (75–80 °F). Discus prefer 28–30 °C; goldfish 18–22 °C. Always match new water to existing tank temperature within 1 °C to avoid stressing fish.
Every hardness and alkalinity conversion routes through ppm as calcium carbonate as a pivot value. Hardness and alkalinity share the same constants because both are reported as calcium-carbonate equivalent: one dGH or dKH equals 17.86 ppm, one meq/L equals 50.04 ppm, and one grain per US gallon equals 17.118 ppm. Temperature is handled on its own track with the exact definitions, °C = (°F − 32) × 5/9 and K = °C + 273.15, rounded to two decimals.
Choose Parameter first, because it rebuilds the Source unit list. Hardness (GH / CaCO₃) offers ppm, °dGH, meq/L and grains per US gallon; Alkalinity (KH) drops the grains option and keeps ppm, °dKH and meq/L; Temperature offers °C, °F and K. The default is 100 ppm hardness, which converts to 5.60 °dGH. The four preset buttons print a target-range reminder for that setup rather than changing any of your inputs.
Those presets are display-only text and any recalculation clears them, so read the range before you convert or press the button again afterwards. There is no pH conversion at all, even though the preset lines quote pH ranges, and no salinity or TDS handling despite the reef preset mentioning specific gravity. The conversions also assume your test kit reports on a calcium-carbonate-equivalent basis, which is standard but worth confirming on the box.
Divide by 17.86. A water report showing 100 ppm as calcium carbonate is 5.60 dGH, and 180 ppm is 10.08 dGH. The results table lists ppm, dGH, meq/L and grains per US gallon together so you can read across from whichever kit you own.
Yes. Both are expressed as calcium-carbonate equivalent, so the same 17.86 ppm per degree applies. Selecting Alkalinity relabels the output and drops grains per US gallon from the unit list, since water-softener units are not used for carbonate hardness.
Pressing Tropical community prints 5–12 dGH, 4–8 dKH, pH 6.5–7.5 and 24–27 °C. Three more buttons cover African cichlids, discus and reef. These are reference ranges shown beneath the result and they do not alter any input value.
Milliequivalents per litre is the laboratory and reef-chemistry unit, where one meq/L equals 50.04 ppm as calcium carbonate. Reef keepers usually see alkalinity quoted in dKH or meq/L, and dosing calculators frequently expect meq/L rather than a ppm figure.
The preset text is written into a separate line that every recalculation clears, so it disappears the moment you change the parameter, source unit or value. Note the range down before converting, or simply press the preset button again afterwards.
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