how much is 1 PPM?

Lab test lingo:  How much is 1 PPM?

Test results — compost analytical reports included — often convey constituent concentrations in parts per million (ppm) or milligrams per liter (mg/L).  Both state the fraction of the tested substance found per one million units of gas, liquid, or solid.

But what does that really mean?  Is 1 PPM a drop in the bucket or a thimble of water in an ocean?

Such infinitesimal amounts can be difficult to visualize, but here are a few examples found on the web that may help:



Sometimes, even smaller concentrations may be reported as parts per billion or micrograms per liter (μg/L).  When you see this term, correlate to:

Know the limits

One of the best analogies is 1 ppm equals one large mouthful in a lifetime of eating.  But it must be said:  just a small bite of the wrong thing can be one bite too many.

That’s why it’s important to always correlate reported concentrations  with the limits deemed safe by regulators and other jurisdictional entities.  Typically, for easy comparison, these ceilings will be reported in an adjacent column on the lab report.