Water Hardness Calculator
Convert EDTA titration data into total hardness expressed as mg/L CaCO₃ and classify the water sample.
Total hardness
62.5 mg/L as CaCO₃
Classification
Moderately hard
How to Use This Calculator
Collect titration data
Perform an EDTA titration, noting the volume of EDTA solution required to reach the endpoint.
Enter EDTA normality
Standardize the EDTA solution and provide its normality (equivalents per liter).
Input sample volume
Record the volume of water sample titrated. Use the same units (mL).
Read hardness and classification
The calculator outputs total hardness and a qualitative category (soft, hard, etc.).
Formula
Hardness (mg/L as CaCO₃) = (A × N × 50,000) / V
A is EDTA volume (mL), N is EDTA normality, and V is sample volume (mL). The factor 50,000 converts equivalents to mg CaCO₃ per liter.
Example
Using 12.50 mL of 0.0100 N EDTA for 100 mL sample yields hardness = (12.50 × 0.0100 × 50,000) / 100 = 62.5 mg/L.
Full Description
Water hardness arises from multivalent cations such as calcium and magnesium. EDTA titrations quantify these ions by forming stable complexes, and the result is typically reported as an equivalent concentration of calcium carbonate.
This calculator simplifies interpretation of titration data, providing both numerical hardness and qualitative classification for household, industrial, or environmental assessments.
Frequently Asked Questions
What indicator should I use?
Eriochrome Black T is commonly used with a wine-red to blue endpoint, but follow your standard method.
Does alkalinity affect the titration?
Buffer the sample to the recommended pH (around 10) to ensure accurate complexation with EDTA.
Can I use molarity instead of normality?
Yes. For EDTA titrations involving divalent ions, 1 M EDTA equals 2 N. Convert accordingly before entering values.
How precise are hardness categories?
Categories are based on common guidelines; local regulations may use different thresholds.
Can I calculate temporary vs permanent hardness?
This calculator provides total hardness. Additional testing is needed to differentiate temporary and permanent hardness.