Recently, I received the following question from a reader …
You refer to labels often when evaluating a feed or mineral product. I am trying to learn to read labels also…. For example, while I know the letters “ppm” stands for “parts per million,” I don’t really know how much that equates to on a feed label! Some labels will indicate “Zinc, Min. 1.20%” and another label will say “Zinc, Min. 7500 PPM. How do I compare those two amounts????
This is such a great question! It does seem impossible to compare these two labels because they are presented differently. However, a percentage is simply parts per hundred. On one label they are telling you that 1.2 pieces of a 100 piece-pie is zinc. On the other label, they are telling you that 7500 pieces of a million-piece pie is zinc. A piece of pie cut into a million pieces is 10,000 times more pieces than a pie that has been cut into 100 pieces. Without even doing the math, in this case, you might guesstimate that 1.2% is more than 7500 ppm, and you would be correct. Typically, if something is presented as ppm, it is a very tiny amount.
Let’s do the math though and see how these two compare when we put them in the same terms. To convert from ppm to percent, divide the ppm by 10,000.
7500 ÷ 10,000 = 0.75%, compared to the product with 1.2% zinc.
If you prefer to multiply rather than divide, you can convert percent to ppm by multiplying the percentage by 10,000 because 1% = 10,000 ppm.
1.2% X 10,000 = 12,000 ppm compared to the product with 7500 ppm
Contrary to what your math teacher told you when you were in school, we do all have a calculator available to us at all times now, and with Siri, I don’t even have to type in anything, which makes this really easy.
However, if you don’t necessarily care about a head-to-head comparison, and you just want to know which one has more, you can easily eyeball it. Since 1% is 10,000 ppm, if one product has less than 10,000 ppm, and the other product has more than 1%, then the one that is presented as a percentage has more of the mineral.