cheers yep seen the charts etc but wanted to be able to work it out for a spreedsheet and for my own peace of mind. it came precalibrated and its less then a month old so should be fine for now but i'll calibrate it eventually. just trying to figure out of i've been overdosing all this time especially if most are saying to EC between about 1.2-1.8 max. also thought my PPM in my tap water was decent at 130 but its not so decent if it then becomes 260 lol. see what i mean? just confusing as fuck might just get an EC pen also