250 ppm water hardness — 14.01 °dH, 14.6 gpg
250 ppm is the same water as 14.01 °dH in Germany, 25 °fH in France, 17.54 °e in England, 14.6 gpg in the United States and 2.498 mmol/L in the lab. On this chart’s scale it counts as very hard.
- ppm (mg/L CaCO₃)
- 250 ppm
- German degree
- 14.01 °dH
- French degree
- 25 °fH
- English degree (Clark)
- 17.54 °e
- grains per US gallon
- 14.6 gpg
- millimoles per litre
- 2.498 mmol/L
Where soft ends and hard begins depends on the standard
The conversions are fixed; the grades are a choice. This chart draws its lines at the widely quoted 60, 120 and 180 ppm — meaning they are our approximation. The German detergent law, WRMG, draws its own at 1.5 and 2.5 mmol/L, that is 150.1 and 250.2 ppm, or 8.4 and 14 °dH. A 150 ppm water is therefore "hard" on this chart and "soft" under that law — the water did not change, the ruler did. Near a boundary, do not settle the question here: read the standard your appliance or your country actually uses.
- Grade on this chartvery hard
- German WRMG grademedium
- Twice as hard500 ppm
- Half as hard125 ppm
- WRMG8.41 °dH · 14.02 °dH
Nearby cells
very hard
Worth knowing
- ppm (mg/L CaCO₃) is the base, and every other unit is a fixed multiple of it.
- °dH is ppm ÷ 17.85, gpg is ppm ÷ 17.12, °fH is ppm ÷ 10, °e is ppm ÷ 14.25 and mmol/L is ppm ÷ 100.09.
- °dH and °fH both read "one degree per 10 mg/L", yet differ 1.78-fold because one counts CaO and the other CaCO₃.
- Grade boundaries differ between standards — the 60, 120 and 180 ppm on this chart are our chosen approximation.
Frequently asked questions
Q. How many °dH is 250 ppm?
14.01 °dH — ppm divided by 17.85. The same water reads 25 °fH in France, 17.54 °e in England, 14.6 gpg in the United States and 2.498 mmol/L as a molar concentration.
Q. Is 250 ppm soft or hard?
On this chart’s scale it is very hard. Under the German WRMG, though, it is medium — that standard draws its lines elsewhere. Close to a boundary, go by whatever standard your appliance uses.
Q. What if the water were twice as hard?
It would be 500 ppm and every one of the six units would double exactly. Conversion is nothing but multiplication, so half of it, 125 ppm, halves every figure, and at 0 ppm every unit reads zero.