The 4.0 vs 5.0 GPA scale explained
The 4.0 scale caps an A at 4.0; a 5.0 scale is a weighted scale where AP/IB A’s count as 5.0. How the two relate, and how to read a GPA above 4.0.
When you see a GPA above 4.0, it’s on a weighted scale. Here’s how the two scales relate.
The 4.0 scale
The standard unweighted scale: A = 4.0, A− = 3.7, B+ = 3.3, down to F = 0.0. Every course is capped at 4.0 regardless of difficulty, so an unweighted GPA can never exceed 4.0. See the full letter-to-points table.
The 5.0 scale
A 5.0 scale is a weighted scale. Harder courses add a bonus — commonly +1.0 for AP/IB and +0.5 for Honors — so an A in an AP class is worth 5.0 and an A in Honors is worth 4.5. Straight A’s in all AP/IB courses produce a 5.0 weighted GPA. Some districts use a 6.0 scale with larger bonuses.
Reading a 4.5
A 4.5 weighted GPA means mostly A’s in weighted (Honors/AP) courses. Its unweighted equivalent is at most 4.0 — the weighting adds the extra half-point. The exact unweighted number depends on which courses carried the bonus.
Converting between them
There’s no single formula, because the conversion depends on how many of your courses were weighted and by how much. The reliable way is to compute both directly: enter your courses in the weighted GPA calculator for the 5.0-scale number, then turn weighting off (or use the unweighted calculator) for the 4.0-scale number. See also weighted vs unweighted GPA.