A conversion is only as good as the authority behind it. Converting a letter to a grade point is exact if you use your own institution's published table. Converting a percentage to a grade point average is exact only where the institution publishes the percentage bands, and converting a cumulative average back into a percentage is not possible at all, because the information was lost at the letter.
GPA conversion that is exact: letters to grade points
Letters to grade points, using the registrar's own table. The University of Toronto goes further and publishes letter, percentage band and grade point in one table, so a Toronto percentage converts to a Toronto grade point exactly: 90 to 100 per cent is A+ and 4.0, 77 to 79 per cent is B+ and 3.3. That is a real conversion because the institution states it, and it applies to Toronto transcripts alone.
What converts only approximately
A percentage from an institution that publishes no bands, an Indian CGPA on a ten-point scale, or a European grade under a distribution-based system. In each case the honest output is a range and the name of the body that gave it, not a single figure. Any converter that returns one number without naming an authority is asserting something no institution published.
What does not convert at all
A cumulative grade point average back into a percentage. The average is a mean of letters, and each letter covered a band of percentages that differed course by course. Turning it back into one percentage invents precision that was destroyed at the moment the letter was awarded, and no registrar will stand behind the result.
Questions people ask about GPA converter
How do I convert GPA to 4.0 scale values?
Use the published table of the institution that issued the grades, or the published conversion of the institution receiving them. Where neither exists, a recognized credential evaluator's statement is the document that will be accepted.
Can a GPA converter 100 to 4.0 be trusted?
Only where an institution publishes the mapping, as the University of Toronto does. Most American registrars publish letters and grade points and no percentage at all.
What can a CGPA to GPA converter tell you?
There is no single answer. Different evaluators and receiving institutions publish different conversions for a ten-point CGPA, and the one that counts is whichever the receiving institution uses. Ask them before doing the arithmetic.