The best way of finding out your level of language proficiency is to take a language proficiency exam that uses a recognised language proficiency framework.
In the UK and Europe, the most widely recognised language framework is the CEFR, which measures language ability along a six-point scale:
A1: Beginner
A2: Elementary
B1: Intermediate
B2: Upper intermediate
C1: Advanced
C2: Proficient
You can determine your CEFR level on your own using a self-assessment grid or certify it by taking an official language exam that uses the CEFR framework, such as the DELE Spanish Diploma exams. Language certifications lend credibility to your language skills and make a valuable addition to most CVs.