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GPG to PPM Calculator: Water Hardness to Grains Conversion

GPG to PPM Calculator 1

According to the Water Quality Association, water hardness classifications are defined as follows: soft water has 0-3.5 grains per gallon (gpg), moderate hardness ranges from 3.5-7.0 gpg, hard water is characterized by 7.0-10.5 gpg, and very hard water is identified as having over 10.5 gpg.

This blog introduces user-friendly tools for this purpose: 

  1. PPM to GPG Calculator, 
  2. Detailed Water Hardness Conversion Table, 
  3. Manual conversion methods.

GPG to PPM Calculator

Simply the move counter to get the GPG for your PPM

GPG to PPM Water Hardness Table

Grains Per Gallon (GPG):Parts Per Million (PPM):Rating
0.06 gpg1 ppmSoft
0.29 gpg5 ppmSoft
0.58 gpg10 ppmSoft
0.88 gpg15 ppmSoft
1.17 gpg20 ppmSoft
1.46 gpg25 ppmSoft
1.75 gpg30 ppmSoft
2.04 gpg35 ppmSoft
2.34 gpg40 ppmSoft
2.63 gpg45 ppmSoft
2.92 gpg50 ppmSoft
3.21 gpg55 ppmSoft
3.51 gpg60 ppmSoft
3.80 gpg65 ppmModerately Hard Water
4.38 gpg75 ppmModerately Hard Water
4.67 gpg80 ppmModerately Hard Water
4.97 gpg85 ppmModerately Hard Water
5.26 gpg90 ppmModerately Hard Water
5.84 gpg100 ppmModerately Hard Water
6.43 gpg110 ppmModerately Hard Water
7.01 gpg120 ppmModerately Hard Water
7.59 gpg130 ppmHard Water
8.18 gpg140 ppmHard Water
8.76 gpg150 ppmHard Water
9.35 gpg160 ppmHard Water
9.93 gpg170 ppmHard Water
10.52 gpg180 ppmHard Water
11.10 gpg190 ppmVery Hard Water
11.68 gpg200 ppmVery Hard Water
14.60 gpg250 ppmVery Hard Water
17.53 gpg300 ppmVery Hard Water
20.45 gpg350 ppmVery Hard Water
23.37 gpg400 ppmVery Hard Water
26.29 gpg450 ppmVery Hard Water
29.21 gpg500 ppmVery Hard Water

Manual Conversion: Understanding the Math

Gain a deeper understanding of water hardness by learning to convert GPG to PPM manually. 

The formula is simple: PPM = GPG * 17.1. 


For instance, converting 5 GPG to PPM: PPM = 5 * 17.1 = 85.5 PPM


This method ensures you can independently verify your water’s hardness level.

Discovering Your Local Water Hardness

With water hardness affecting many U.S. homes, identifying your area’s level is key. Water hardness charts by state or city and local water authorities provide essential data. Visit this Amazing go-to resource on Water Hardness by state and zip-code

Tips for Accurate Water Hardness Measurement

Grains Per Gallon (GPG)Parts Per Million (PPM)Water Hardness Rating
0.00 - 3.51 GPG0-60 PPMSoft Water
3.57 - 7.02 GPG61-120 PPMModerately Hard Water
7.08 - 10.53 GPG121-180 PPMHard Water
10.58+ GPG181+ PPMVery Hard Water

FAQs for PPM to GPG Water Hardness Conversion

1. How do I convert GPG to PPM for water hardness?

To convert grains per gallon (GPG) to parts per million (PPM), multiply the GPG value by 17.1. For instance, 5 GPG equals 85.5 PPM.

2. What does grains hardness to PPM mean?

Grains hardness to PPM refers to converting the hardness measurement from grains per gallon, a traditional unit, to parts per million, a more widely used unit.

3. How are grains of hardness converted to PPM?

Similar to converting GPG, multiply the grains of hardness value by 17.1 to convert it to PPM.

4. Can you explain water hardness grains to PPM conversion?

Water hardness measured in grains (per gallon) can be converted to PPM by multiplying the grain value by 17.1, providing a standardized measurement.

5. What is the grain to PPM conversion process?

The conversion process involves multiplying the number of grains (per gallon) by 17.1 to get the equivalent parts per million (PPM).

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