There isn't one universal conversion method that applies here because the scale and the way the GPA is computed can vary based on the school that you are attending!
Generally though a 4.0 GPA is equivalent to 100%, meaning that each tenth of a GPA point corresponds to a specific percentage.
The calculation I would do for a 2.26 GPA is to take
(2.26 - 2.0) x 10 = 0.26 x 10 = 2.6
Generally a 2.0 corresponds to a "C" or 70% so then this would be about a 70% + 2.6% = 72.6% grade, meaning that it would be in the low C to C+ range.
I hope that helps get you moving in a good direction on this one! Feel free to reach out if you have any additional questions beyond that :)
