Alkalinity Converter: ppm, dKH, meq/L
Convert alkalinity between ppm, dKH and meq/L. Type a reading in any unit and see the rest.
Alkalinity (KH)
- dKH
- 8
- ppm (mg/L as CaCO₃)
- 142.9
- meq/L
- 2.857
How the conversion works
Alkalinity is reported in three common units, and they are all fixed multiples of each other:
- 1 dKH = 17.86 ppm (mg/L as CaCO₃) = 0.357 meq/L
- 1 meq/L = 2.8 dKH = 50 ppm
So to go from dKH to ppm, multiply by 17.86. To go from dKH to meq/L, divide by 2.8. Going the other way, ppm divided by 17.86 is dKH, and meq/L times 2.8 is dKH.
The ppm figure is always “as calcium carbonate”, the way water chemists express alkalinity, so it is the same number as mg/L as CaCO₃.
dKH, ppm and meq/L for common alkalinity levels
| dKH | ppm as CaCO₃ | meq/L |
|---|---|---|
| 4 dKH | 71.4 ppm | 1.43 meq/L |
| 6 dKH | 107.1 ppm | 2.14 meq/L |
| 7 dKH | 125 ppm | 2.5 meq/L |
| 8 dKH | 142.9 ppm | 2.86 meq/L |
| 9 dKH | 160.7 ppm | 3.21 meq/L |
| 10 dKH | 178.6 ppm | 3.57 meq/L |
| 11 dKH | 196.4 ppm | 3.93 meq/L |
Typical alkalinity ranges
| Water | dKH | ppm | meq/L |
|---|---|---|---|
| Natural seawater | 6.4 to 7 dKH | 114 to 125 ppm | 2.29 to 2.5 meq/L |
| Reef tank, typical target | 7 to 11 dKH | 125 to 196 ppm | 2.5 to 3.93 meq/L |
These are common targets, not rules. Species differ, and in a reef tank a steady value matters more than the exact number, so avoid swings of more than about 1 dKH in a day.
Why test kits report different units
Hobby test kits often report alkalinity in dKH, lab and some digital checkers report ppm or mg/L, and reef literature uses meq/L. They describe the same property of the water. If a dosing instruction or a target from one source is in a different unit than your kit, convert your reading rather than the target, so you are comparing like with like.
Frequently asked questions
How many ppm is 1 dKH?
One dKH is 17.86 ppm of alkalinity as calcium carbonate (CaCO₃).
How do I convert dKH to ppm?
Multiply the dKH by 17.86. For example, 8 dKH is 142.9 ppm.
How do I convert dKH to meq/L?
Divide the dKH by 2.8. For example, 8 dKH is 2.86 meq/L, and 7 dKH is 2.5 meq/L.
Is dKH the same as KH?
Yes. KH is carbonate hardness, and dKH is KH in degrees (German degrees, deutsche Karbonathärte). Aquarium keepers use KH and alkalinity interchangeably.
How many ppm of alkalinity does a reef tank need?
Most reef keepers aim for about 7 to 11 dKH, which is 125 to 196 ppm, and keep it steady. Natural seawater is about 6.4 to 7 dKH.
More calculators
- Saltwater mix calculatorGrams of salt for your RODI water, by brand, for the salinity you choose.
- Salinity converterSpecific gravity, ppt and conductivity, corrected for temperature.
- Aquarium volume calculatorReal water volume from dimensions, minus rock and sand.
- Water change calculatorHow a reading falls after a water change, and how many it takes.
These calculators give estimates for general guidance. Confirm what matters, like salinity and alkalinity, with a test and your own equipment before you adjust a tank.