Water Hardness Calculator
Convert water hardness between ppm, mg/L, gpg, and dGH instantly.
Enter Hardness Value
Based on calcium carbonate equivalence (CaCO₃)
Converted Values
Enter a value to convert.
Hardness Guide
- 0 – 60 ppm: Soft
- 61 – 120 ppm: Moderately Hard
- 121 – 180 ppm: Hard
- 180+ ppm: Very Hard
Water Hardness Calculator – Convert mg/L, PPM, GPG & °dGH
This Water Hardness Calculator helps you convert between the most common water hardness units: PPM (mg/L), GPG, and °dGH. Water hardness measures minerals like calcium and magnesium in water.
Conversion Factors
- 1 GPG = 17.12 PPM (mg/L)
- 1 °dGH = 17.848 PPM (mg/L)
Why water hardness matters
- Clogs household pipes & reduces appliance life
- Causes soap scum & poor lather
- Affects aquarium water chemistry
- Impacts laundry & skin comfort
Water hardness classification
- 0–60 ppm: Soft
- 61–120 ppm: Moderately Hard
- 121–180 ppm: Hard
- 180+ ppm: Very Hard
Use this tool to evaluate whether water softening or conditioning treatment is needed for your home, industry, or aquarium.