I am feeding my plants at PH 6.4 and when I try to measure TDS it shows 1.65 PPT- the meter automatically switches from PPM to PPT when I put it in the water/nute mix.

Are my old math skills correct, this is a move the decimal point type conversion? 1.65ppt = 1650ppm?

I am feeding 1/4tsp of fox farm nutes (open sesame and chaching) per 30oz of water, 2x each per plant so a total of 1/2tsp nutes and 60oz water per plant. This should be on the high end of the recommended dosage but still low on the ppm (assuming my math is correct).

Thoughts? Input? Corrections?


Ok searching I believe u have it right or seems right. 5000ppm is a 5.00ppt reading. So a 0.001ppm reading would be a 1pp0ppm read according to google lol. Just Google ppm to ppt conversions

I tried confirming my math online but all the calulators I found were using the acronym “PPT” for parts per trillion which obviously takes the conversion way off, in the wrong direction…

Yeah, “parts per thousand” isn’t intuitive. But yes, that’s the correct way to convert it.

[This is the reason the USA needs to get on the metric system, doggone it already!]

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I use it everyday :+1: so much simpler


Yes you are correct. Once you go over 1000ppm, it switches to PPT

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I was in grade school the last time they tried to get metric in the USA. They were idiots about the way they did it - making us convert the measurements, what the heck for? Gimme meterstick and I’ll get down to business.

Since I taught science, I got to work in metric and teach the kids. SO much easier!

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825 i think, just watched a YouTube video, you time’s that number by 50 if i listened correctly. Wait for others opinions :slight_smile:

Metric is simpler to learn, and is in line with the rest of the entire world. If they had done it in 75, the cost and “pain” of the switch would be well behind us now.

It’s costly to have to maintain two sets of tools, which is needed because most stuff made now outside the USA - which is most of it - is metric. I have imperial and metric tools, it’s flat out foolish and a huge waste of money.

“We’ve always done it that way” is the nonsense I heard when I was a cadet.

Sorry, but we’ll have to agree to disagree. I think it’s horrifically shortsighted.

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I use the pc60 and had a issue with this for a bit also lol you have it right tho to convert ppt to ppm just simply get rid of the decimal point i hate how it automatically converts over to ppt once you hit 1000ppm the conductivity does the same also it will switch to microsiemens to milisiemens