# Finding Parts Per Million (Ppm)

Everyone gets very confused when they try to learn how to convert from g/l or mg / l, or mg / g, or something similar, to ppm. However, the process is almost identical to finding a percentage. To find a percentage (parts per hundred), you take the part, and the total and do the following:

percentage of part in total $= \frac{\mathrm{part}}{\mathrm{total}}\times 100$ %

To find ppm (parts per million), you take the part, and the total and do the following:

parts per million $= \frac{\textrm{part}}{\textrm{total}}\times 1 000 000$ ppm

Notice any similarities there?

For example, suppose after a fire we have 1 g of carbon in every litre of water in some pond. (I don’t know if this is realistic. Don’t criticise me… =P) We first convert everything to the same units. 1 litre of water is approximately 1000 g. Now, we can find the percentage of carbon in the water:

percentage $= \frac{1\,\textrm{g C}} {1000 \,\textrm{g H_{\textrm{2}}O}}\times \,\,100$% $= 0.1$ %

And the ppm of carbon in the water:

ppm $= \frac{1\,\textrm{g C}} {1000 \,\textrm{g H_{\textrm{2}}O}} \times 1 000 000 \,\, \textrm{ppm} = 1000$ ppm

Simple right?