Filter boxes are covered in numbers and terms — “1 micron”, “activated carbon”, “NSF 53”, “5-stage”. This tool decodes them in plain English, one at a time. No jargon, no assumptions. Start anywhere.
A micron (µm) is one thousandth of a millimetre. A filter’s micron rating is the size of particle it’s designed to catch. The key thing to know up front: a smaller number means a finer filter — a 0.5 micron filter catches smaller things than a 5 micron one. Move the slider to see what a given rating stops, and what slips through.
Particle sizes are approximate ranges drawn from published health and water-industry references (WQA, CDC, utility data). Real organisms vary; the scale shows typical sizes to build intuition, not exact cut-offs.
Two filters can both say “1 micron” and perform very differently, because the rating comes in two kinds. This one word changes what the number actually promises.
Per the U.S. CDC: some nominal 1-micron filters can allow 20–30% of 1-micron particles (such as Cryptosporidium) to pass, while an absolute rating is the more consistent barrier. If a filter lists a micron number with neither word, the rating type isn’t specified.
Pick something written on a filter you’re looking at. You’ll get what it means, what it does, and — just as importantly — what it doesn’t do.
Marketing phrases aren’t regulated the way certifications are. Here’s what each one describes, stated plainly, so you can judge what it’s telling you.
Now that the specs make sense, put them to work: