Micron Ratings Explained, and What the Number Means

A micron is a tiny unit of length, and a filter's micron rating is about the size of the openings in it. This page explains the unit. It can't give you ratings for particular robots, because none of the saved sources list them.

What a micron is

The micrometre is one millionth of a metre. It's also known as the micron¹. The symbol is μm.

For scale, the same source says the width of a single human hair ranges from approximately 20 to 200 μm¹. The same list puts a typical bacterium at 1 to 10 μm long¹. Both are small, and the bacterium is the smaller of the two.

A rating is only a size. It doesn't say how much a filter holds, how fast it clogs, or how it should be cleaned.

Mesh and openings

A general reference on filtration describes surface filters as solid sieves with a mesh to trap solid particles². A mesh has openings. Anything bigger than an opening is held back, and anything smaller can pass through.

That's the idea behind a micron rating. The number describes the opening, so a lower number means a finer screen. Check the maker's spec sheet or manual for your robot's own figure, since this site doesn't have one to quote.

Pool filters and particle sizes

Here's a real figure from a related type of equipment. Suction-side and pressure-side cleaners depend on the pool's main filter. One article says that means they can't remove particles smaller than the pore size of the pool's existing filter element. It gives a range, from under 5 μm for diatomaceous filters to 50+ μm for sand filters³.

That is about the pool's main filter, not a robot's own filter. Robots, the same article says, work apart from the pool's main filter and pump³. Their filter is a separate part with its own openings. Don't read those numbers as a robot's rating.

Why "finer" isn't the whole story

Fine and coarse each have a place in the idea, but this page can't say which suits which debris. None of the saved sources match mesh sizes to leaves, sand or silt. If a maker's manual does, that's the place to read it.

The filtration reference does make one general point: a depth filter is less prone to clogging than a surface filter because of its greater surface area for trapping particles². It says nothing about robots, so treat it as background only.

What this means for you

Two points hold regardless of model.

A finer opening catches smaller particles. This follows from how a mesh works².

Your manual or the maker's spec sheet is where a real rating lives. If it lists one, you can compare it against the numbers above. If it doesn't, you can ask the maker.

The robot as a whole is described on the opening page.