Enter the ORP (Oxidation-Reduction Potential) value in millivolts to calculate the approximate chlorine level in parts per million (ppm).

ORP to Chlorine Level Formula

The formula to convert ORP to chlorine level is not straightforward as it depends on various factors such as pH and temperature. However, for the purpose of this calculator, a simplified linear approximation is used:

Chlorine (ppm) = (ORP - 650) / 200


  • ORP is the Oxidation-Reduction Potential value (mV)
  • Chlorine is the chlorine level (ppm)

To calculate the chlorine level, subtract 650 from the ORP value and then divide by 200. This provides an estimated chlorine level in ppm.

What is ORP?

ORP stands for Oxidation-Reduction Potential, which is a measure of the cleanliness of the water and its ability to break down contaminants. ORP levels are measured in millivolts (mV) using an ORP meter. A higher ORP value indicates a greater ability to oxidize and thus disinfect contaminants, which is often associated with higher levels of chlorine.

How to Calculate Chlorine Level from ORP?

The following steps outline how to estimate the chlorine level from an ORP measurement.

  1. First, measure the ORP value of the water using an ORP meter.
  2. Input the ORP value (in mV) into the calculator.
  3. Use the simplified formula provided above to estimate the chlorine level in ppm.
  4. Click the “Calculate” button to get the estimated chlorine level.
  5. Use the result as a guideline for understanding the disinfection potential of the water.

Example Problem:

Use the following variables as an example problem to test your knowledge.

ORP value (mV) = 750 mV

Using the simplified formula, the estimated chlorine level would be:

Chlorine (ppm) = (750 – 650) / 200 = 0.5 ppm