Microns: What They Mean to Water Filters

Not all water filters were created equally. Find out what a micron is, and why they are so important to water filters.

Microns and Water Filters

A micron, as defined by dictionary.com is:

Also called micrometer. The millionth part of a meter. Symbol: μ, mu.”

In slightly more understandable terms, one millionth of a meter works out at 0.0001 cm or 0.001 mm. A human hair is around 0.0889 mm and there are 25,4000 microns in one inch.




You might ask what this little science lesson has to do with water filters? Well most filters can have their effectiveness at removing pollutants measured by how low their micron score is. For example, a water filter that protects down to 1 micron, will block any particles larger than this from passing through. Anything smaller than 1 micron may continue through and be part of your drinking water.


Water pollutants come in a variety of shapes and sizes, and by knowing exactly what you’re looking for, you stand a much greater chance of stopping it. The table below shows some common water pollutants and their sizes in microns.


Water Pollutant Particle Size (Microns)
Mold Spores 10 – 30
Asbestos 0.7 – 90
Insecticide 0.5 – 10
Bacteria 0.2 – 10
Lead 0.1 – 0.7
Viruses 0.004 – 0.1


Note the size of virus particles. These include E.coli, hepatitis, and legionnaires disease. For a water filter to protect against the smallest virus particles, it would need to have a filter capable of working down to below 0.004 microns. Actually, to be guaranteed protection then an ultraviolet filter would be needed too. The only methods of home water filtration that work on this scale are reverse osmosis, and distillation. Now water distillation cannot be measured in microns, but reverse osmosis can. An RO membrane can filter down to an amazing 0.0001 microns or 0.00000001 cm. Compare this with the most effective whole house filter that I am aware of, the Aquasana Rhino, which fights water contaminants down to 0.35 microns, and a typical carbon filter which could work from anywhere between 0.5 – 20 microns.

Each system has it’s positive and negative aspects, and the micron rating is not the only thing to be considered when buying a home water filter. For example, a problem with chlorine would not require such strict filtration. Be aware though, that just any old water filter will not be a solution to water pollution for every problem. Certain contaminants will only be removed by certain water filter types. Make sure you know exactly what is wrong with your water before you commit to buying a home water filter

We specialize in whole house and reverse osmosis water filters here at Water Filter Answers. Please follow us on Facebook, Twitter, and Google+ to stay up to date with the latest news and reviews in the water filter world.


Centers for Disease Control and Prevention

Environmental Protection Agency

Water Quality Association


  1. It looks like you have a typo in your Micron graphic. You have .001 Inches equals .00254mm and .001 Inches equals .0254mm (can’t be both).
    By my math:

    and you are implying that the large dot is only 10 times bigger than the smaller dot – sure looks more 100 times. Also while I am pointing things out – if the outer circle represents a human hair and is only 3.5 times bigger than the large dot inside the circle the scale is off pretty far.
    Just sayin’ – Looks wrong.

  2. E.coli is a bacteria, not a virus. I stopped reading there because your credibility just went to 0.

  3. Thank you for this brief lesson about microns and what they mean to water filters; it was useful to me. There are a couple of mathematical errors in the comparison diagram “How Big is a Micron” which appears to credited to Pinterest – please accept this notice as a gentle and well-meaning notice. The solid circle referenced as 0.00254 mm is equal to 0.0001 inches rather than 0.001 inches. The 1 Micron diameter circle is equal to 0.000039 inches rather than 0.000036 inches.
    Kind regards.

Leave a reply