I conisder that DuoLingo is one of the best sites on the Internet for learning languages, first beacuase it's completely free and second due to provides you an excellent gramitical practice.
Recently, Duolingo has launched the "Test Center" where you can take a verified exam that costs 20$ and gives you a brief indicator of your english level.
Also, you can practice whith quick and free exams, that gives you an estimate puntuation of your level (similar to the verified ones)
The question here, is how these results relate to another testing methods like TOEFL?
Duolingo has carried out an investigation to determinate the correlation between with the results of TOEFL and the Duolingo test.

Please note that now the results are given in percentage, for example if you got a 63% score on the Duolingo Exam, your puntuation will be 6.3


Maybe some of you know the CEFR, which I consider a great tool for describing your knowledge of a language, so you can use the next table to converse the puntuation of TOEFL to the CEFR level.
Becuse there are different converstions of the TOEFL score, I've deciced to take it from the official page of TOEFL, which converts the score to the IELTS score. (Also I've decided to do this, because in the TOEFL official page the maximum level is C1)
Finally, the IELTS score to the CEFR scale.





Practical example.
As you have seen, it's pretty difficult to obtain accurate results, so I am going to use an example to explain how to obtain the CEFR score.

Imagine that I've obtained a 65% on the Duolingo exam, so first  I am converting it to 6.6, which results in a score of 95-98  on the TOEFL exam (first table), that means a 7 on the IELTS. Finally 7  equals to a C1 level.