EC to PPM Converter

Convert EC to PPM on the 500, 640, and 700 scales at once, or go from a PPM reading back to EC.

EC (mS/cm) 1 mS/cm = 1,000 µS/cm. If your meter reads µS/cm, divide by 1,000.

Which scale is my meter?

Scale	Factor	Common on
500 (NaCl)	1 mS/cm = 500 ppm	Hanna, Milwaukee, most US pen meters
640	1 mS/cm = 640 ppm	Eutech, some European meters
700 (KCl)	1 mS/cm = 700 ppm	Bluelab Truncheon, some Australian meters

EC 0.00 mS/cm 0 µS/cm

PPM (500 scale): 0
PPM (640 scale): 0
PPM (700 scale): 0
Stage range

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EC reference by growth stage (hydro and coco)

Stage	EC (mS/cm)	PPM 500	PPM 700
Seedlings / clones	0.4 to 0.8	200 to 400	280 to 560
Early veg	0.8 to 1.4	400 to 700	560 to 980
Late veg	1.4 to 2.0	700 to 1,000	980 to 1,400
Early flower	2.0 to 2.4	1,000 to 1,200	1,400 to 1,680
Late flower	2.4 to 2.8	1,200 to 1,400	1,680 to 1,960

PPM is a converted estimate. Meters measure conductivity and multiply by a fixed factor, so two meters on different scales will show different PPM for the same solution. Compare EC when in doubt.