AP Biology exam review: format, the 8 units, and how to study

What’s on the AP Biology exam

The AP Biology exam splits evenly into two sections worth 50% apiece. The first gives you 90 minutes for 60 multiple-choice questions. Some stand alone; the rest come in clusters of four or five built around one shared stimulus, usually a data table, a graph, or a described experiment. College Board weights all six of its science practices across that section, and is careful to say the figures apply to the multiple choice alone: concept explanation 25–33%, argumentation 20–26%, visual representations 16–24%, and questions and methods, representing and describing data, and statistical tests at 8–14% each.

The six free-response questions, and what each is worth

The second section gives you another 90 minutes for 6 free-response questions. College Board names every one of them and publishes its point value, which almost no other guide does:

• Question 1, Interpreting and Evaluating Experimental Results. 9 points, weighted 1, 3, 3 and 2 across parts A to D.
• Question 2, Interpreting and Evaluating Experimental Results with Graphing. 9 points, weighted 1, 4, 2 and 2.
• Question 3, Scientific Investigation. 4 points, one per part.
• Question 4, Conceptual Analysis. 4 points, one per part.
• Question 5, Analyze Model or Visual Representation of a Biological Concept or Process. 4 points, one per part.
• Question 6, Analyze Data. 4 points, one per part.

Every question has exactly four parts, A to D, and the six add to 34 raw points. College Board prints no total, so 34 is the sum of six figures it does print. Both nine-point questions go by the same name, but their four parts are weighted differently, and only Question 2 asks you to build a graph. Its Part B is the largest single part on the exam, and College Board is not consistent about it: the exam tables put four points on that part, while its own guidance on how graphs are scored says up to three are earned for a correctly constructed graph. Both statements sit in the current Course and Exam Description.

The calculator, the equation sheet, and how the exam is delivered

You may use a basic four-function model with a square root key, or a scientific one, on both sections, and College Board is explicit that it has to be nongraphing. Bluebook carries a Desmos scientific calculator of its own. Beginning with the 2027 exam, any handheld that can store data is barred, graphing models included. AP Biology and AP Environmental Science are the only two exams College Board names in that restriction.

The equation sheet is not only statistics. It runs two pages and carries the mean, standard deviation and standard error formulas with a chi-square table, the laws of probability, the Hardy–Weinberg equations, four separate growth models, a diversity index, water and solute potential, and the surface area and volume formulas. AP Biology sits among nine subjects that get their reference material on paper, shipped to schools ahead of the exam, so a printed copy reaches your desk on the day. You may write on it, nothing you write on it is scored, and it stays in the room. Our AP Biology formula sheet sets out every equation by topic.

Delivery is hybrid rather than fully digital. The multiple choice is answered inside Bluebook, and the free-response prompts are read there too, but the answers themselves go into paper booklets by hand.

The 8 units of AP Biology

AP Biology is organized into eight units that build from molecules to ecosystems, and College Board publishes a weighting for each. It states twice, in the course framework and again in the exam information, that these are weightings on the multiple-choice section rather than on the exam as a whole. Natural Selection is the single heaviest at 13–20%: no other unit starts as high or reaches as far. Cellular Energetics and Gene Expression tie for second at 12–16%.

Across both sections the course is organized around four big ideas, which College Board lists as Evolution, Energetics, Information Storage and Transmission, and Systems Interactions. Each of the four short free-response questions is set on its own big idea and its own unit, so between them they reach four corners of the course. Unit 7 rewards the deepest read, and our explainer on Darwin natural selection sets out the mechanism, the conditions it assumes, and the types it produces.

How AP Biology is scored

Your multiple-choice and free-response points are combined into one composite score, which College Board converts to a 1–5. It is not a curve. The AP Biology Course and Exam Description states that AP exams are criterion-referenced rather than norm-referenced, so every student who meets the criteria for a score receives it, however many students that is. College Board publishes no cut scores and no conversion table for this exam.

In 2026, 71% of students came away with a 3 or better, and 15% reached a 5. The last complete year is fuller: in 2025, 70.4% of 287,232 students scored 3 or higher, with a mean of 3.24. Set against the 40 exams College Board reported for 2026, that puts AP Biology 23rd on pass rate, a little below the field average of 73%.

Where the free-response points are actually lost

College Board publishes a mean score for every free-response question, and in its Chief Reader Report a mean for every individual point. In 2025 students earned 17.05 of the 34 free-response points between them, or almost exactly half the section.

The pattern is not the one most study guides describe. Question 2, the graphing question, was the highest scoring of the six at 5.17 of 9. Question 6, Analyze Data, was the lowest at 1.70 of 4. Point by point the gap is starker still. The best-earned point on the 2025 exam, at 0.89, asked students to identify which proteins the data showed increasing; the worst, at 0.02, asked them to justify a claim about why. The four graph-construction points on Question 2 averaged 2.89 of 4 between them. The two justification points on Question 1 averaged 0.16 of 2.

Drawing the graph is where students do best. Saying why is where the points go.

To see what a practice raw score turns into, run it through our AP Bio calculator.

How to study for AP Biology

Lead with understanding rather than memorization, and let College Board’s own data tell you where that pays. Every free-response part is built on a task verb: describe, identify, analyze, construct, state, predict, justify, explain. Students reliably earn the describing and identifying points and reliably lose the justifying ones, so the marginal point on this exam is almost always an explanation rather than a fact.

That makes the free response the place to spend your practice, since it is half the exam. Work past questions against the rubric with our AP Biology FRQ guide. Take the units singly, using the AP Biology Progress Check MCQ and FRQ answers, which walk through the Progress Checks your teacher assigns in AP Classroom. And brush up on the high-yield ideas with our AP Bio topics.

When you write, answer the verb you were given. A part that says describe wants the thing named and characterized; a part that says justify wants the reasoning that connects your answer to the data or the biology, stated in full. The 2025 results suggest most students stop one sentence short of that.

When is the AP Biology exam, and how long is it?

The 2027 AP Biology exam is on Monday, May 3, 2027, in College Board’s Session 2, which starts at 12 p.m. local time in the lower 48 states, Hawaii and Washington, D.C. (11 a.m. in Alaska). A school can begin an exam up to an hour after its listed start time. The exam runs 3 hours. Confirm the details with your AP coordinator, and against College Board’s own exam calendar, before you plan around it.

What you can carry in is narrower than most students expect. The reference information is provided, so you do not bring your own, and College Board’s exam-day rules bar books, notes, dictionaries, highlighters and any reference guide of your own.