Reef unit converter
Test kits, brands and forums use different units. Convert alkalinity between dKH, meq/L and ppm, salinity between ppt and specific gravity, gallons to litres and Fahrenheit to Celsius.
Formulas and sources last checked . How we check
Calculator
Result
8.00 dKH is8.00 dKH
- dKH
- 8.00
- meq/L
- 2.853
- ppm as CaCO3
- 142.8
- Calcium a coral uses with it
- 57.2 ppm
How do I convert dKH to meq/L and ppm?
1 dKH is 17.848 mg/L of alkalinity expressed as calcium carbonate (Wikipedia, carbonate hardness), and 1 meq/L is 50.04 mg/L as calcium carbonate. So 1 meq/L is 2.804 dKH. Red Sea rounds this to 2.8 in its manuals; the difference is under 0.2 per cent. Salinity and specific gravity are linked by the standard UNESCO seawater equation (EOS-80): 35 ppt is SG 1.0264 at 25 C. A US gallon is 3.785 litres; a UK gallon is 4.546 litres.
dKH = meq/L x 2.804ppm as CaCO3 = dKH x 17.848 = meq/L x 50.04litres = UK gallons x 4.546 = US gallons x 3.785F = C x 9 / 5 + 32
Worked example: a US guide says 3 meq/L
- 3 meq/L x 2.804 = 8.4 dKH, or 3 x 50.04 = 150 ppm as calcium carbonate.
- Corals that use that much alkalinity also use about 8.4 x 7.15 = 60 ppm of calcium, because they build skeleton from both in a fixed ratio.
- A 75 US gallon tank is 75 x 3.785 = 284 litres, but only 62 UK gallons.
What are the limits?
Other calculators
- Salt mixGrams of salt for a batch, and what your refractometer or hydrometer should read.
- Salinity correctionHow much water to swap, day by day, at a safe pace.
- Water change effectWhat a change, or a run of changes, does to a reading.
- ATO reservoir safetyHow far salinity falls if a stuck pump empties the reservoir.
- Dosing from a test resultMillilitres to bring alkalinity, calcium or magnesium back to target.
- Daily consumptionHow much your tank uses a day, and the daily dose to match.
- Tank volumeLitres from the tank size, and the net water after rock, sand and sump.
- Heater sizeWatts for a UK room, split across heaters so one stuck on is not a disaster.
- Light hours and PARPhotoperiod, ramps, daily light and PAR by coral group.
- Electricity running costWhat the tank costs to run at the current UK price cap.
- Stocking and compatibilityCheck a list of fish against each other, the tank and your corals.