To find this information, I recommend checking these resources:
* IMDb: The Internet Movie Database (IMDb) usually lists ratings and certificates for movies.
* Rotten Tomatoes: This website aggregates reviews and provides a "Tomatometer" score for movies.
* Metacritic: Another site that compiles reviews and provides a "Metascore".
* Official movie websites: The official websites of the movie distributor or production company often have this information.
* Regional film classification boards: The ratings and certificates will vary depending on the region. You can find information on the websites of organizations like the MPAA (US), BBFC (UK), or equivalent boards in other countries.
Good luck in your search!