Water hardness converter
Convert between ppm, German degrees, French degrees and grains per gallon, the units on water reports and softener settings.
That's 1.67× as hard as moderately hard water, while hard water is 1.2× harder. That counts as hard water: expect limescale in kettles and showers.
What it means
How hard is that water?
All scales measure the same thing, calcium carbonate content, just with different sized degrees.
Every unit
Your hardness in every unit
Learn
Three things worth knowing
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1 °dH is about 18 ppm
German degrees are the biggest: 1 °dH = 17.8 ppm. French degrees are exactly 10 ppm, and a grain per gallon is 17.1 ppm.
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Why soap made it matter
Hard water reacts with soap to make scum instead of lather. Nineteenth-century chemists measured hardness by how much soap it took to make foam.
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Hard water is not unhealthy
It scales kettles and spoils lather, but the calcium and magnesium in it are nutrients. Softeners replace them with sodium, which is the trade-off.
Shortcuts
Popular hardness conversions
Background
About hardness units
Hardness is dissolved calcium and magnesium, reported as if it were all calcium carbonate. Water companies use ppm (mg/L), Germany uses °dH, France °fH, and American softeners grains per gallon.