I have my GPA in the 100 point system, how could I calculate it in 4.0 point system? I searched, and I didn't find a good answer,
You should ask your university if they could provide a mapping to a 4-point system. If they don't, you simply have to calculate GPA*4/100! In case you feel this undermines your prospects, ask your university for a rank certificate which will give the admissions committee a good idea of where you stood in your department.
Unless it is specifically requested, do not do it. Some school even urge you not to do it. It is highly probable, that they know your scale and understand what level means you are smart and hard working. Be sure to include thing like cum laude, merit scholarships, ranking within the cohort, ... These things are easier for them to understand and help them to compare you to the other students.
Miscalculating your GPA may result in unintentional deception or undermining your actual achievements. Be careful.
I know this already has an accepted answer but still:
If you need it for grad school, chances are that the university would want "untouched" grades. In other words, they want to see your grades "as is" without any modifications, conversions or other such activities. I had my GPA on a 10 pt scale and most universities asked me to enter it as it is and that the job of conversion would be their headache.
If a university needs converted GPA, chances are that it provides a conversion algorithm. For instance, University of Washington provided this (Warning! PDF) to international students. I've seen Berkeley, PSU and a few other universities do something similar.
Columbia University provided the reference for WES, a GPA Conversion tool.
Citatation : IEOR Dept.
Excerpt of the passage (In case the link dies):
For the online application, though, you can enter an approximate conversion of your percentage grade. There are many websites that help you with grade conversion, and one of them is available through WES. Please note that we do not recommend this site over other ones.
Warning: Do not use random GPA conversion schemes from blogs or shady websites. While it might not cause much difference, don't risk it.
I found the following conversion for Syria, 100 point systems differ so generally the conversion is not always the same. I would use this only as an indicator.
| Scale | Grade Description | US Grade | Notes | 95.00 - 100.00 | الشرف (Honor) | A+ | Arabic: Sharaf | 85.00 - 94.99 | امتياز (Excellent) | A | Arabic: Imtiyaz | 75.00 - 84.99 | جيد جداً (Very Good) | B+ | Arabic: Jayed Jeddan | 65.00 - 74.99 | جيد (Good) | B | Arabic: Jayed | 60.00 - 64.99 | مقبول (Aceptable) | C | Arabic: Maqboul | 0.00 - 59.99 | راسب (Fail) | F | Arabic: Raseb; Lowest passing grade
According to this source: http://www.classbase.com/Countries/Syria/Grading-System
I recently had to deal with this situation when applying. My University did not have an A/B/C... system and would not provide a GPA.
Some of the application forms that I filled out provided instructions for international students, eg: no not enter a GPA. So I would start by reading the application forms.
For those that do not, my strongest recommendation is to contact the person in charge of applications at the department that you are applying to. Ask them what you should do in your specific circumstance. There is usually an email address on the department website for application enquiries.
Unfortunately a few universities never replied to my emails. For their applications I left the GPA field blank if the form allowed. For forms that required a GPA for submission I simply made up what I thought was an appropriate system.
While this didn't seem to hurt my chances, I would only recommend this as a last resort if you can't get a straight answer from the department you are applying to.