What TDS measures
TDS stands for total dissolved solids. It represents dissolved minerals, salts, metals, and other dissolved substances in water.
TDS is commonly reported in mg/L or PPM, especially when the sample is dilute water.
How meters estimate TDS
Many handheld meters do not directly weigh dissolved solids. They measure electrical conductivity and apply a conversion factor.
Because dissolved ions conduct electricity differently, TDS readings should be treated as useful estimates unless confirmed by laboratory methods.
Using TDS with calculators
A TDS to PPM calculator is helpful when a meter or report provides mg/L and you need a PPM interpretation.
For hydroponic or aquarium use, pair TDS readings with the EC to PPM calculator when you need to understand meter scale assumptions.
Frequently asked questions
Is TDS the same as PPM?
TDS may be reported in PPM, but TDS describes total dissolved solids while PPM is the concentration unit.
Why do TDS meters differ?
Meters can use different EC-to-TDS conversion factors, so readings may vary between devices.