There are many ways to show the difference in language knowledge including Common European Framework of Reference (CEFR), British IELTS or American TOEFL but you could also check your approximate language level online. Understanding of your language level could help you in the job search and further education planning.
Tests and language levels comparison
Complex online English tests
Tests of this kind include questions from different language knowledge areas: listening, reading, grammar, vocabulary. Thus this is one of the most objective way to understand your English level for free. The only obvious disadvantage is that speaking cannot be tested during these online tests.
Knowledge of grammar is essential for any further language study. The following tests give you an opportunity to evaluate your English level without spending a lot of time. The results will not be precise certainly, but it could provide you some basic information on your English.