Water Hardness PPM To GPG Calculator (+ PPM To GPG Chart)

Water hardness in the US is measured either in ppm (parts per million) or gpg (grains per gallon).

Parts per million, also referred to as American degrees, is a water hardness unit equal to 1 mg/L CaCO₃ dissolved in water.

Grains per gallon is also a water hardness unit defined as 1 grain of CaCO₃ dissolved in water.

We have created two useful resources for ppm to gph conversion:

1. ppm To gpg Water Hardness Calculator. Just insert ppm, and the calculator will dynamically determine the equivalent gpg water hardness. For the reverse conversion, you can use this gpg to ppm calculator.
2. ppm To gpg Water Hardness Chart. We have converted 1 to 1000 ppm into gpg, and summarized the results in the chart below. We have denoted soft water (0-60 ppm) with this green color, moderately hard water (61-120 ppm) with this light blue color, hard water (121-180 ppm) with this blue color, and very hard water (181+ ppm) with this dark blue color.

In order to convert ppm to GPG, you can use this converter:

How To Convert PPM To GPG?

The common denominator between ppm and gpg is a reference to water hardness measured as a quantity of CaCO₃ dissolved in water.

Here is a formula that enables you to calculate gpg from ppm:

gpg = ppm/17.118

In essence, if you divide parts per million by 17.118, you get grains per gallon. Factor 17.118 comes from the volumetric and mass difference between the water hardness units.

Thus every 1 gpg is equal to 17.118 ppm (1 gpg = 17.118 ppm).

Water hardness calculations are most relevant for water softener systems.

Water Hardness PPM To GPG Chart