EC is the direct measurement
Electrical conductivity measures how well a solution conducts electricity. Nutrient solutions conduct electricity because dissolved ions carry charge.
PPM readings from EC meters are estimates created by multiplying EC by a conversion factor.
Why conversion factors differ
Common scales include 0.5, 0.64, and 0.7. A single EC reading can therefore produce different PPM values depending on the meter scale.
That is why EC-to-PPM calculators must show the selected factor instead of assuming one hidden standard.
Best practice for growers
Track trends with the same meter and factor. Avoid comparing PPM values from different meters unless the scale is known.
When sharing recommendations, include EC and the conversion factor so another grower can interpret the number correctly.
Frequently asked questions
Which EC-to-PPM factor should I use?
Use the factor that matches your meter scale. If unsure, check the meter documentation.
Is EC better than PPM?
EC is the direct measurement. PPM is often easier to discuss but depends on a conversion factor.