Read this straight off your product’s label. Most say “per gallon” or “per liter,” so enter 1 here to match. A label dosing every 2 gallons would use 2 instead.
That’s the label’s base dose scaled to 87.5% for vegetative (75-100% of label dose).
EC ↔ PPM Converter
The math:
PPM = EC × scale factor (500, 640, or 700)
500 scale
900
Hanna, Milwaukee, GH, Oakton
640 scale
1,152
Some European meters
700 scale
1,260
Bluelab, Eutech, Truncheon
Which PPM scale does my meter use?
Scale
Common meter brands
500
Hanna, Milwaukee, General Hydroponics, Oakton
640
Some European meters
700
Bluelab, Eutech, Truncheon
EC is the reliable number. It’s the international, meter-agnostic measurement of conductivity. PPM is a convenience conversion that depends entirely on which scale your meter uses. Treat EC as your primary reading, and use this converter only when you need to translate someone else’s PPM-based chart or feeding schedule into a number your meter will actually show.