College Board publishes, for every AP course, the share of the exam each unit is worth. It is in the Course and Exam Description, it is free, and it is the single most actionable number in AP preparation — and most revision plans never look at it.
The consequence is a specific, common mistake: a student ranks their units by accuracy, finds the one with the lowest percentage, and spends the week there. If that unit happens to be worth 8% of the paper while another unit at a similar accuracy is worth 24%, they have just spent their week on a third of the points they could have.
The numbers are not close
In AP Microeconomics, unit 3 is 22%–25% of the exam and unit 6 is 8%–13%. In AP Calculus BC, infinite sequences and series alone is 17%–18% while limits and continuity is 4%–7%.
At equal accuracy, an hour spent on the heavier unit is worth roughly three times as much on the paper. Ranking by accuracy alone cannot see that, because accuracy says nothing about what the question is worth.
The same arithmetic in the units you already study
How to build the ranking yourself
- Find your course's Course and Exam Description on AP Central and write down each unit's published weight range.
- For each unit, write the share of questions you are currently missing. If you have not attempted a unit at all, leave it blank — that is not zero, it is unknown, and treating it as zero is how unopened units disappear from a plan.
- Multiply the miss rate by the weight. That product, not the accuracy, is what the unit is costing you on the real paper.
- Do the unopened units separately. They have no measured cost, but they have a published weight, and a large unopened share means your ranking is only describing the part of the exam you have seen.
Two things this arithmetic cannot do
It cannot tell you what order to learn in. A course builds on itself — unit 5 of Calculus assumes unit 3 — so if you are learning the material for the first time, follow the course order. Exam weight decides where to spend time once you already have evidence about yourself; it does not decide what to learn first.
It also cannot turn into a predicted score. College Board does not publish the composite cut points, and they move every year with exam difficulty, so any calculator promising you a 4 from a practice percentage is extrapolating from an old released worksheet. Weighting your revision is useful. Predicting your score is not something the published data supports.
Common questions
Where do I find AP unit weights?
In your course's Course and Exam Description, published free by College Board on AP Central. The 'Course at a Glance' pages list each unit's exam weighting as a range.
Why is the weight a range and not one number?
College Board publishes a range because the exact mix varies between administrations. Any source giving you a single percentage per unit has picked a midpoint and not told you.
Should I study my weakest unit first?
Not automatically. Multiply how much of the unit you are missing by what the unit is worth on the exam. A moderate gap in a heavily weighted unit usually costs more than a large gap in a light one.
Knowing you are losing points is not the same as knowing which ones
algₐ reads every answer you give and names the specific rule you keep breaking — and says so plainly when it does not have enough evidence to name anything yet.
