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Hydroponics · Calculator

EC / PPM converter

Switch readings between EC, 500 scale, 640 scale, and 700 scale. Because not all meters speak the same language.

EC and PPM converter
Underlying conductivity. The honest number. 1 mS/cm is 1000 µS/cm.
US hobby meters. Bluelab pens, HM Digital.
Many European meters and commercial gear.
Bluelab truncheons, some Eutech.
EC (mS/cm) --
500 scale --
640 scale --
700 scale --
Change any field, the others update live. If you only know one scale, type it and read the rest off.

Why this exists

PPM is calculated from EC using a conversion factor. Different meters use different factors (500, 640, 700). The number on the display means different things depending on the brand. This tool converts between them so you can compare numbers across meters or follow a guide that uses a different scale than your meter does.

EC is the actual physical measurement. If you're unsure which scale to use, report and target EC and ignore PPM entirely.

Some meters read EC in µS/cm rather than mS/cm (1600 instead of 1.6). Pick µS/cm next to the EC box, or just type the reading; anything above 20 is treated as µS/cm, since no nutrient solution gets anywhere near 20 mS/cm.

Related tools

Further reading