The bonus points
On the most common weighting system, honors classes add +0.5 and AP or IB classes add +1.0 to that class's grade points. So an A in an AP class counts as 5.0 instead of 4.0 on your weighted GPA.
Unweighted GPA is unaffected
Your unweighted GPA still caps an A at 4.0 regardless of class difficulty. That's why students often have a weighted GPA above 4.0 and an unweighted GPA at or below it.
Is it worth it?
Generally, yes — colleges value course rigor, and a slightly lower grade in a challenging class is often viewed more favorably than an easy A. Just avoid overloading to the point where your grades slip across the board.
The honest trade-off is worth doing on paper. On the common +1.0 AP system, a B in an AP course is worth 4.0 weighted — the same as an A in a standard course. So swapping a standard A for an AP B costs you nothing in weighted GPA while adding rigor. Swapping it for an AP C, worth 3.0 weighted, does cost you.
What happens to the weighting at college
It disappears. Weighted GPA is a high-school construct: colleges recalculate from your transcript using their own method, and once you enrol, your college GPA runs on a plain 4.0 scale with no bonus for difficulty.
That has a practical consequence students rarely anticipate. A student arriving with a 4.3 weighted high-school GPA is not starting college with a 4.3 — the ceiling is now 4.0 at most schools, and at many an A+ is capped at 4.0 too, so there is no way to bank surplus points at all.
AP exam scores are a separate thing entirely
Your AP course grade and your AP exam score do different jobs. The course grade goes on your transcript and into your GPA; the exam score, from 1 to 5, does not affect your GPA at any point.
What the exam score can do is earn college credit, which is often worth more than the GPA bump. A qualifying score can let you skip a prerequisite entirely — and note that credit earned by examination typically carries no grade points, so it raises your credit total without moving your college GPA in either direction.
Check how your school actually weights
There is no national standard. The +1.0 for AP and +0.5 for honors pattern is common but far from universal — some districts add 0.5 for both, some cap the weighted GPA at 5.0, some weight only certain departments, and some do not weight at all.
Ask your counsellor for your school's specific policy before planning a schedule around GPA effects. A course load optimised against the wrong weighting table is worse than one chosen on interest and rigor.