EC to PPM Conversion Chart for Hydroponics (500 & 700 Scale)
Home > Hydroponic Systems > EC to PPM Conversion Chart for Hydroponics (500 & 700 Scale) Last Updated: July 2026 | Reviewed for electrolytic mobility, sodium chloride vs potassium chloride conversion factors, and temperature compensation Quick Answer: Electrical Conductivity (EC measured in mS/cm) is the universal, scientifically accurate measurement of dissolved fertilizer salts in hydroponics. Meters display Parts Per Million (PPM) by multiplying EC by an arbitrary conversion factor: either the 500 Scale (Hanna / NaCl standard: $ ext{EC} imes 500$) or the 700 Scale (Truncheon / KCl standard: $ ext{EC} imes 700$). For example, an EC of 2.0 mS/cm equals 1,000 PPM on the 500 scale but 1,400 PPM…