To obtain an official certificate of your level, you have to sit a DELF (A1-B2) or DALF (C1-C2) exam in person. There are plenty of unofficial tests online that you can use to gauge your level, such as: 

1. https://delfdalf.ch/index.php?id=292&no_cache=1 ;

2. http://www.languagelevel.com/french/ ;

3. http://www.french-exam.com/mock-french-exam/

Bonne chance!