The most common formula, and why it isn't universal
Percentage = CGPA × 9.5 is the formula most Indian students encounter first, since it's used by several large universities on a 10-point CGPA scale. But it's a per-university convention, not a nationally mandated rule — other universities use different multipliers, and some use an entirely different formula shape, such as Percentage = (CGPA − 0.75) × 10. There is no single authority that fixes one formula for every Indian university or board.
A worked example showing the gap between formulas
For a CGPA of 8.2: the ×9.5 formula gives 8.2 × 9.5 = 77.9%. The (CGPA − 0.75) × 10 formula gives (8.2 − 0.75) × 10 = 74.5%. That's a 3.4 percentage-point gap for the exact same CGPA, purely from which formula is applied — a gap large enough to matter for eligibility cutoffs (scholarships, further-study admissions, some government job applications) that specify a percentage threshold rather than a CGPA threshold.
Why this matters beyond curiosity
Many external forms — scholarship applications, foreign university admissions, some recruitment eligibility criteria — ask for a percentage even when your marksheet only shows CGPA. Using the wrong formula for your specific university can misrepresent your actual percentage, in either direction. When in doubt, check whether your university publishes an official CGPA-to-percentage conversion formula (many do, in their examination regulations or on the official transcript itself) rather than assuming the ×9.5 default applies.
When your marksheet already shows both
Some universities print both CGPA and an equivalent percentage directly on the official transcript — in that case, use the printed percentage rather than recalculating it yourself, since the university's own conversion is authoritative for its own students. Recalculating only matters when you have a CGPA-only marksheet and need a percentage figure for an external form that doesn't accept CGPA directly.
Sanity-checking your multiplier
If you're unsure of your university's exact formula, a reasonable sanity check is that most Indian 10-point CGPA-to-percentage multipliers fall somewhere between 9 and 10 — a result far outside that range (well under 70% for a CGPA above 8, for example) is a sign the multiplier being used doesn't match your university's actual convention.