Electric Conductivity (EC

Water Quality, Metallurgy & Electric Conductivity Metrology

Electric Conductivity is the intrinsic measure of a material's or aqueous solution's ability to conduct an electric current:

• **

• Universal Electric Conductivity Conversion Formulas (ASTM Standards)**:

1 S/m = 10^-6 MS/m = 0.010 S/cm = 10 mS/cm = 10,000\ μS/cm (EC)

1 MS/m = 10^6 S/m = 10^4 S/cm = 10^10\ μS/cm

100\% IACS 58.00 MS/m = 5.80 × 10^7 S/m (ASTM B193 Copper standard)

• **

• Aqueous Water Quality & TDS Equations**:

TDS = EC_μS/cm × k_tds (where k_tds ≈ 0.65 for natural water)

ρ = (1) / (σ_e) (Bulk Resistivity in Ω·m) | Water Resistivity (MΩ·cm) = (1) / (EC)_μS/cm × 10^6

• **

• Standard Environmental & Material Conductivity Benchmarks**:

• Ultrapure Type I Water: 0.055\ μS/cm 18.2 MΩ·cm Theoretical limit of pure H_2O

• Municipal Drinking Water: 500.0\ μS/cm 0.050 S/m 325 ppm TDS

• Hydroponic Nutrients: 2.0 mS/cm = 2,000\ μS/cm 1,300 ppm TDS

• Ocean Seawater (35 ppt): 50,000.0\ μS/cm = 5.0 S/m 32,500 ppm TDS

• Electrical Pure Copper: 58.0 MS/m = 5.8 × 10^7 S/m 100.0\% IACS

How to Use This Calculator

Enter your Electric Conductivity (σ / EC) (e.g. 58 in σ), From Conductivity Unit — choose from MegaSiemens per Meter (MS/m = 10⁶ S/m - Metallurgy / Metals), Siemens per Meter (S/m - SI Base Unit), MicroSiemens per cm (µS/cm = EC - Water Quality Standard), To Conductivity Unit — choose from % IACS (International Annealed Copper Standard), MegaSiemens per Meter (MS/m), Siemens per Meter (S/m), Water TDS Conversion Factor (k_tds, 0.50–0.70) (e.g. 0.65 in factor), and Material & Environmental Water Benchmark — choose from Custom Conductivity Solution/Material, Electrical Copper (58.00 MS/m = 580,000 S/cm) → 100.0% IACS | ρ = 1.724 × 10⁻⁸ Ω·m, Ocean Seawater (50,000.0 µS/cm = 5.0 S/m) → 50.0 mS/cm | 35 ppt salinity | TDS ≈ 32,500 ppm. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Formula Reference: Electric Conductivity (EC) & Water TDS Calculator

Input variables:

electricConductivityMagnitudeInput — Electric Conductivity (σ / EC)

sourceConductivityUnitSelect — From Conductivity Unit

targetConductivityUnitSelect — To Conductivity Unit

tdsConversionFactorInput — Water TDS Conversion Factor (k_tds, 0.50–0.70)

Computed outputs:

convertedTargetConductivityValue — Converted Target Conductivity

standardSiSiemensPerMeter — Conductivity in SI (S/m)

waterEcMicrosiemensPerCm — Water EC (MicroSiemens/cm = µS/cm)

iacsConductivityPercent — Metallurgy Conductivity in % IACS

estimatedWaterTdsPpm — Estimated Total Dissolved Solids (TDS)

Mathematical relationships extracted from calculation logic:

IACS_BASE_CONDUCTIVITY = 58001276.03; // S/m for 100% IACS copper

ecUsCm = sigmaSm * 1e4

iacsPercent = (sigmaSm / IACS_BASE_CONDUCTIVITY) * 100.0

tdsPpm = ecUsCm * tdsFactor

rhoMohmCm = (safeDiv(100.0, sigmaSm)) / 1e6; // MΩ·cm for water

Reference constants:

IACS_BASE_CONDUCTIVITY = 58001276.03

Standard: IAB and MMA digital advertising metric definitions

Worked Example

A water treatment plant operator measuring an electrical conductivity of 500 µS/cm in municipal tap water converts this to 0.050 S/m and calculates an estimated Total Dissolved Solids (TDS) concentration of 325 ppm.

Understanding Your Result

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