Filter Beta Ratio Calculator

Inputs

Start from

Beta ratio (β)

Default result

Beta ratio(β)

200

Pass

At or above the β = 200 (99.5%) level commonly marketed as an absolute rating.

β ≥ 75 is the common minimum for a "rated" filter; β ≥ 200 is the typical absolute-rating threshold.

Also computed

Capture efficiency(η)99.5%

Passed per million challenged5,000

The linear way to read β: 1,000,000 ÷ β particles get through.

Method notes 4 notes

Definition math from the ISO 16889 multipass test: β(x) = upstream ÷ downstream counts at particle size x. The rating is meaningless without its size — β200 at 10 µm and at 3 µm are different filters.
Efficiency compresses near 100% while contamination does not: β200 → 99.5% and β1000 → 99.9% sound close, but the β200 filter passes five times as many particles.
Real circuits recirculate: system cleanliness settles where ingression and capture balance, so target ISO 4406 cleanliness codes drive the β you need — the maker's data sheet maps one to the other.
Dirt-holding capacity, pressure-drop growth and bypass cracking are the other half of filter selection and live in the catalog, not this ratio.