If you are in an industry that requires you to measure the TDS (total dissolved solids) in a water solution, you may sometimes get a measurement that uses parts-per-thousand (PPT) rather than parts-per-million (PPM) on your Apera tester.

It is important to know that 1000 PPM = 1.0 PPT. They are the same measurement made different by only 3 decimal places.

So for example, if you get a reading of 1.86 PPT, that would be 1860 PPM.

It is similar to if you are measuring distance in feet. Eventually, once you have thousands and thousands of feet, you can instead measure in miles. It is the same principle here. Large numbers are transformed into smaller more manageable numbers yet still mean the same thing; 10,560 feet is 2 miles. 2000 PPM is 2 PPT.

Most Apera testers will switch from PPM to PPT at the point it reaches 1000 PPM. It does this because even the most inexpensive of our meters are capable of testing up to 10,000 PPM. That number is too large for the 4 digit display on our instruments, so we must convert these measures into smaller numbers for ease and convenience. That is why we include the PPT measurement unit.

Here are some more examples to help clarify the relationship between these 2 measures:

1500 PPM = 1.5 PPT

1750 PPM = 1.75 PPT

2.5 PPT = 2500 PPM

3.95 PPT = 3950 PPM

By remembering this simple math conversion, you will never be lost when reading measurements with PPT.