Each course's letter grade is looked up in a fixed table mapping A+ through F to standard 4.0-scale grade points, multiplied by that course's credit hours to get quality points; the GPA is total quality points divided by total credits, recalculated every time you edit a row.
FAQ
Why do A+ and A both equal 4.0 instead of A+ being worth more?
This follows the standard U.S. 4.0 scale, where 4.0 is the ceiling — some schools do give A+ a value above 4.0, like 4.3, but that's a less common variant, so this calculator uses the conventional capped scale.
What happens if I leave a course's credit hours at 0?
It's included in the list but contributes nothing to the GPA — 0 credits means 0 quality points and 0 weight in the total-credits denominator, so it neither helps nor hurts your average.
Free, unlimited, no account. If this saved you a paid tool, a small thanks is appreciated.