dGH to ppm converter
Convert between dGH and ppm for both general hardness (GH) and carbonate hardness (KH). Same conversion applies to both.
Updated 30 July 2026
dGH to ppm conversion table
One degree of general hardness is 17.86 ppm, so converting either way is a single multiplication. These tables cover the range aquarium test kits report; use the calculator above for anything in between.
dGH to ppm
| dGH | ppm | GH band |
|---|---|---|
| 1 dGH | 18 ppm | Very soft |
| 2 dGH | 36 ppm | Very soft |
| 3 dGH | 54 ppm | Very soft |
| 4 dGH | 71 ppm | Soft |
| 5 dGH | 89 ppm | Soft |
| 6 dGH | 107 ppm | Soft |
| 7 dGH | 125 ppm | Soft |
| 8 dGH | 143 ppm | Moderate |
| 9 dGH | 161 ppm | Moderate |
| 10 dGH | 179 ppm | Moderate |
| 11 dGH | 196 ppm | Moderate |
| 12 dGH | 214 ppm | Hard |
| 13 dGH | 232 ppm | Hard |
| 14 dGH | 250 ppm | Hard |
| 15 dGH | 268 ppm | Hard |
| 16 dGH | 286 ppm | Hard |
| 17 dGH | 304 ppm | Hard |
| 18 dGH | 321 ppm | Very hard |
| 19 dGH | 339 ppm | Very hard |
| 20 dGH | 357 ppm | Very hard |
| 22 dGH | 393 ppm | Very hard |
| 25 dGH | 447 ppm | Very hard |
| 30 dGH | 536 ppm | Very hard |
ppm to dGH
| ppm | dGH | GH band |
|---|---|---|
| 50 ppm | 2.8 dGH | Very soft |
| 75 ppm | 4.2 dGH | Soft |
| 100 ppm | 5.6 dGH | Soft |
| 125 ppm | 7.0 dGH | Soft |
| 150 ppm | 8.4 dGH | Moderate |
| 175 ppm | 9.8 dGH | Moderate |
| 200 ppm | 11.2 dGH | Moderate |
| 250 ppm | 14.0 dGH | Hard |
| 300 ppm | 16.8 dGH | Hard |
| 350 ppm | 19.6 dGH | Very hard |
| 400 ppm | 22.4 dGH | Very hard |
| 500 ppm | 28.0 dGH | Very hard |
The bands are general hardness (GH) categories, which is what determines whether a species will thrive. Carbonate hardness (KH) converts identically but is read against different functional ranges, because it describes pH stability rather than fish suitability. Switch the calculator to KH for those bands.
How the conversion works
The conversion factor is 1 dGH = 17.86 ppm. This is a fixed chemistry-based ratio: degrees of hardness measure the same dissolved minerals as ppm, just on a different scale.
The same conversion applies to both general hardness (GH, which measures all dissolved minerals primarily calcium and magnesium) and carbonate hardness (KH, which measures only the carbonate and bicarbonate fraction). Test kits typically report results in one unit or the other depending on where they were made. European kits favour degrees, while American and Australian kits favour ppm.
What the numbers mean for fishkeeping
GH and KH affect different aspects of your tank:
GH (general hardness) determines which fish species will thrive. Soft-water species like neon tetras and discus struggle in hard water; hard-water species like guppies and snails struggle in soft water. See our water parameters guide for the full breakdown, or our best freshwater fish for Australian tap water guide for region-by-region picks.
KH (carbonate hardness) determines how stable your tank's pH is. Low KH tanks are prone to pH swings and crashes; high KH tanks resist change. KH is functionally a pH stability measurement rather than a fish-welfare measurement.
For most freshwater community tanks, you want GH in the moderate range (140 to 210 ppm / 8 to 12 dGH) and KH at moderate or higher (70+ ppm / 4+ dGH) for parameter stability.
Why categorisation matters more than exact values
A test reading of "180 ppm GH" is functionally identical to "10 dGH GH": both are moderate-hardness water suitable for most community species. Don't get hung up on whether your test kit reads in degrees or ppm; convert it once, identify the category, and choose species suited to that category.
For browsing species suited to your specific water profile, use the species directory's hardness filter after converting your test reading.