mS/cm to ppm Converter

By: Patrick Myers Patrick Myers is the CEO and Founder of Calculator Academy. He has over eight years of experience developing online calculators and holds a B.S. in Mechanical Engineering. His work focuses on formula implementation, calculator accuracy, unit conversions, and creating practical tools that are easy to use.

Last Updated: July 3, 2026
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This calculator was built with Calculator Academy’s community calculator studio with AI assistance, and was reviewed by the Calculator Academy team before publication.

About the mS/cm to ppm Converter

This converter estimates total dissolved solids in ppm from an electrical conductivity value entered in mS/cm. It is useful for hydroponics, water quality checks, aquariums, irrigation, and anyone comparing EC readings to common TDS meter scales.

How to use this calculator

  1. Enter the conductivity value in mS/cm.
  2. Select the TDS conversion scale: 500, 640, or 700.
  3. Read the estimated ppm result.
  4. Review the µS/cm, selected factor, and equivalent dS/m values.
  5. Compare the table to see what the same conductivity equals on the other scales.

How it works

The calculator first converts conductivity from millisiemens per centimeter to microsiemens per centimeter. Since 1 mS/cm equals 1,000 µS/cm, the entered value is multiplied by 1,000.

It then estimates ppm using the selected TDS factor. The formula is ppm ≈ mS/cm × 1,000 × factor, where the factor is 0.50 for the 500 scale, 0.64 for the 640 scale, or 0.70 for the 700 scale.

The result is an estimate because electrical conductivity measures how well a solution conducts electricity, while ppm represents dissolved solids inferred from that conductivity. Different dissolved salts and different meters use different conversion factors, so lab-grade reporting should follow the scale specified by the instrument or standard method.

Example calculation

If conductivity is 1.000 mS/cm and the 500 scale is selected, the calculator converts 1.000 mS/cm to 1,000 µS/cm. It then multiplies 1,000 by 0.50, giving an estimated TDS of 500 ppm. On the same conductivity, the 640 scale would show 640 ppm and the 700 scale would show 700 ppm.

Frequently asked questions

How do you convert mS/cm to ppm?

Multiply the mS/cm value by 1,000 to get µS/cm, then multiply by the chosen TDS factor: 0.50, 0.64, or 0.70.

Why do different scales give different ppm values?

PPM is estimated from conductivity, and different meters assume different dissolved solid compositions. The 500, 640, and 700 scales use different conversion factors.

Is 1 mS/cm always equal to 500 ppm?

Only on the 500 scale. At 1 mS/cm, the estimate is 500 ppm on the 500 scale, 640 ppm on the 640 scale, and 700 ppm on the 700 scale.

Is mS/cm the same as dS/m?

For these units, the numeric value is the same: 1 mS/cm equals 1 dS/m.

Which TDS scale should I choose?

Use the scale specified by your TDS meter, test method, or application. If you are matching another reading, use the same scale that instrument uses.