Well free of charge usually provide by ur institution or college.

else there is a free for students .. here a link with top 10 free  , some are online checker and some have software to download ..good luck with choosing one .

http://elearningindustry.com/top-10-free-plagiarism-detection-tools-for-teachers

You will find many free plagiarism checking sites. But from my own experience I feel it is waste of time as it also doesn't check the articles which are not freely available on net.

You can try this by coping a paragraph of already published article (not available free online) and check in these free plagiarism softwares. Check in 4-5 different free sites. You will know the result.

I strongly suggest you to use any of the licensed Plagiarism softwares. For a long time I tried with free softwares but of no use. Now I am using turnitin and it is one of the best.

If you are not able to access the licensed version, still you have got one option.

You can request someone who has access to licensed versions to plagiarism check for you

Dear Khaled Saad,

The link is really very useful. Thanks for sharing it.

Respected Sir, please Check following links

https://plagiarismcheckerx.com/plagiarism-checker-for-students

https://www.duplichecker.com/

https://www.plagscan.com/en/

https://seomagnifier.com/online-plagiarism-checker

https://www.writemypaper.net/free-plagiarism-checker-students-online/

https://www.paperrater.com/plagiarism_checker

https://smallseotools.com/plagiarism-checker/

http://www.checktext.org/

https://www.scanmyessay.com/

http://www.paperrater.com/plagiarism_checker

http://www.plagtracker.com/

But Turnitin is most popular Plagiarism Checker.

You can try this website https://www.oxphrase.com/

oxphrase is an accurate online plagiarism checker for students, teachers and researchers.

It’s super easy to use and can export readable plagrism report as PDF.

I hope it can helps you.