Most colleges are familiar with IB scores, and adjust them onto conventional grading scales. Some colleges will award half a point for SL classes, and a full point for HL, but others will weight them all an entire point. That is, a B+ in an IB HL course will be weighted as a 4.3 (or A+); an SL course might or might not: it could be weighted as an A-. The colleges know how to adjust the 7-point IB system, but they won’t all do it identically. Depending on the colleges he’s looking at, you should probably inquire with the individual admission offices.
If the IB courses are given letter grades, then do the following:
Use the Roger Hub UC GPA calculator. Count up all your grades: A’s, B’s, C’s etc… for all the a-g course requirements taken in 10-11th grades. Input the # of semesters of IB classes taken 10-11th grades.
The calculator will give you the UW UC GPA, Capped Weighted UC GPA and Fully Weighted UC GPA.