All calculatorsTDS Calculator (Total Dissolved Solids)
Compute TDS (mg/L, ≈ ppm) from electrical conductivity using a configurable factor (TDS = k·EC), or from gravimetric data (residue mass & sample volume). Includes steps, a mini chart, and a quality gauge.
Background
TDS estimates the total mass of dissolved ions per liter of water. Two common determinations: (1) EC-based estimate via TDS = k·EC, where EC is in µS/cm (or mS/cm) and k depends on ionic makeup; (2) Gravimetric determination via drying and weighing residue: TDS (mg/L) = mass (mg) / volume (L).
How to use this calculator
- Choose method: EC-based (needs EC and k) or Gravimetric (needs mass and volume).
- We convert units automatically and report TDS in mg/L (≈ ppm).
- Toggle sig-fig, show steps, mini chart, and a quality gauge.
Formula & Equation Used
EC method: TDS (mg/L) = k × EC(µS/cm)
Unit note: 1 mS/cm = 1000 µS/cm
Gravimetric: TDS (mg/L) = mass (mg) / volume (L)
Example Problems & Step-by-Step Solutions
Example 1 — EC method
EC = 500 µS/cm; k = 0.50 → TDS = 0.50 × 500 = 250 mg/L.
Example 2 — Gravimetric
Mass = 10.0 mg; Volume = 250 mL = 0.250 L → TDS = 10.0 / 0.250 = 40.0 mg/L.
Frequently Asked Questions
Q: Is mg/L the same as ppm?
For dilute aqueous solutions (≈1 g/mL), mg/L ≈ ppm.
Q: What k should I use for EC→TDS?
Commonly 0.50–0.65 depending on ionic composition; 0.50 is a common general default.
Q: Does the gauge indicate potability?
No — it’s an indicative taste/quality band only. Check local standards for drinking water limits.
