Get a ballpark figure on a filters horsepower rating.
There are two figures
MAX & Nominal
MAX is the maximum horsepower application we would use this filter for. It should give a ralatively long service life and good filtration from an air flow point of view.
The nominal horsepower rating is the power level which puts the air filter under very slow stress. Which means good filtration (because air is not being sucked so quickly through the filter) and good service life (because the filter is so big, you should be able to use it for extended periods without worrying about cleaning it).
Enter the size of the filter you are looking at to get the power rating.
These figures are approximate
The figures do not treat paper air filters differently
The figures do not take into consideration weather
The power figures are a ball park figure only. Ultimately you should use a vacuum gauge to determine if your air filter is causing a restriction (between the air filter and the turbo on a turbocharged car).