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Unit converter for fishkeepers
Type a value into any field and the other units update straight away. Handy for test kits, forums and instructions from other countries.
The conversions
- Hardness: 1 °dH = 17.85 mg/L CaCO₃ (ppm) = 0.178 mmol/L. US test kits and forums usually give GH and KH in ppm: 8 °dKH is about 143 ppm.
- KH in meq/L: 1 meq/L = 2.8 °dKH. In reef tanks the value is often called “alkalinity”, typically 7 to 9 °dKH, i.e. 2.5 to 3.2 meq/L.
- Conductivity and TDS: TDS meters convert conductivity with a factor, usually 0.5 to 0.7. The calculator uses 0.64. So compare values from the same meter where possible.
- Gallons: 1 US gallon = 3.785 litres, 1 UK gallon = 4.546 litres. A US “20 gallon” tank holds about 76 litres.
- Temperature: °F = °C × 9 ÷ 5 + 32. 25 °C is 77 °F.
In the app: everything in one unit
Aqualizer stores your readings consistently and works out derived values such as CO₂ from KH and pH or the toxic share of ammonia itself.
- 11 water parameters with target ranges
- CO₂ from KH and pH
- Toxic NH₃ from ammonia, pH and temperature
Coming soon to Google Play – try it now
Join the beta on Android
Unit FAQ
How do I convert °dH to ppm?
Multiply by 17.85. 10 °dH is about 179 ppm (mg/L CaCO₃). The other way round, divide ppm by 17.85.
Is °dGH the same as °dKH?
The unit is the same (German degrees), but it measures something different: GH is general hardness (calcium and magnesium), KH carbonate hardness (bicarbonate). Both convert to ppm the same way.
How many litres is a 10 gallon aquarium?
US gallons are almost always meant: 10 × 3.785 = just under 38 litres. In UK gallons it would be 45 litres.
How do I convert conductivity to TDS?
With your meter’s factor, usually between 0.5 and 0.7. With 0.64, 500 µS/cm is about 320 ppm TDS.