The Biology CLEP can be a bit hard to prep for because there is a lot to memorize. Study times vary a lot for this exam. One user reported studying for around 100 hours and scored a 63; someone who took high school bio a year earlier crammed for two days and passed with a 62. Most people will be somewhere in the middle of that. You need a 50 out of 80 to pass at most schools, though some set the bar at 60, so check yours before you book a date.
3 Top Prep Resources
- Best free course: Modern States Biology
- Best Reddit thread: How I studied for the Biology CLEP
- Best video set: Bozeman Science's AP Biology Video Essentials
Best Reddit threads for the Biology CLEP
How I studied for the Biology CLEP is the one to read first. The writer put in roughly 100 hours, passed with a 63 out of 80, and laid out the exact resources they used. The comments are almost as good as the post itself. One reader passed with a 62 after two days because they had taken bio in high school; another walked in cold, needed a 45, and got a 51.
Passed 14 CLEPs in 2 months (AMA) treats Biology as one stop on a crazy study bonanza. Their advice: watch a video on every topic listed on the College Board biology page, then take some practice tests. They ended up earning a 58. This thread also teaches how to get Peterson's tests for free.
"clep biology" (2026) is short but recent. That poster passed with a 61.
Free Biology CLEP books, courses & study sites
Modern States Biology is where you start if for no other reason than that you can get your exam for free. The course runs three modules that mirror the exam's three sections, about 4 hours of video plus a heavy set of readings. Finish the module quizzes and Modern States mails you a voucher that pays the $97 exam fee AND the testing-center seat fee. Free course, free exam. The one catch is depth: the videos stop short of the exam on a few topics, so this is your starting frame and NOT your only source. Do every module quiz, even for the parts you already know. The voucher only unlocks after all of them are done.
College Board's official materials. Two pieces are worth grabbing free: the exam page with the full topic outline, and a set of 9 official sample questions with an answer key.
Khan Academy AP/College Biology is free and the closest thing to a real course with built-in practice questions. It is strongest on cell biology, genetics, evolution, and ecology. It is thin on the plant structure and vertebrate organ systems that the CLEP does test, so do not presume you know everything if this is the only course you use.
OpenStax Biology 2e is a free college textbook (read online, PDF, or audiobook) which is similar to what you would need for a classroom biology course. This covers everything you will need plus a whole lot more. Use it more as a reference to study sections you are having particular difficulty with.
Quizlet: the "BIOLOGY CLEP" deck follows the College Board outline almost line by line (organelles, macromolecules, membranes, enzymes, cell division, genetics). Free to flip through although it is much less informative than our biology study guide flashcards.
Best YouTube videos for the Biology CLEP
Bozeman Science: AP Biology Video Essentials is Paul Andersen's 56-video set, and it is the closest thing on YouTube to the CLEP outline. One concept per video and he is a great teacher. It was recorded for an earlier AP course, so it looks dated, but cell biology and genetics have not changed, and plenty of r/clep passers ran these at 1.5x or 2x speed.
Crash Course Biology (2012) is Hank Green's 40-episode run, following the AP Biology curriculum plus some anatomy. This is much more brief and can be used to figure out what topics you need more time studying rather than as a full course.
Amoeba Sisters make cartoons that walk through one topic at a time. Reach for them when a written explanation isn't working but you don't need a full course.
Dr. Matt & Dr. Mike are often chosen for the metabolism and physiology topics which can be hard for a lot of students. Glycolysis, the Krebs cycle, homeostasis, and the organ systems are all covered. They go slower and further than some of the other videos mentioned above.
Advice from Degreeforum
There is one more pool of feedback worth knowing about. On DegreeForum's members-only exam board, the Biology thread has gathered years of first-hand reports. Expect a stack of Punnett-square and Mendelian genetics questions. Know your mitosis and meiosis phases cold, and be ready to read graphs, since one 2025 passer counted a dozen questions built on just four graphs. Plant and flower reproduction turns up more than people expect, and the Peterson's practice tests run harder than the real exam, which makes them a strong gauge of readiness. One subscriber who passed with a 62 put it plainly: "This is very doable, but on the harder side of the CLEP exams." That board is included with your InstantCert membership, so joining gets you both the study guide and the forum where people post exactly what they saw on the exam.
How to put it all together
Here is a three-week version that lines up with what works for many students, assuming a couple of focused hours most days. Stretch it to five or six weeks if biology is new to you. First, get our biology study guide, run through the questions, and see if that is enough.
Week 1. Work through Modern States Modules 1 and 2 (molecular, cellular, and organismal biology) and take the quizzes so you can get the voucher in the mail. Use the videos that match for any topic that doesn't click right away.
Week 2. Finish Modern States Module 3 (population biology, evolution, ecology). Start the Quizlet deck for vocabulary and keep OpenStax open to look up anything you're having problems with.
Week 3. Switch to testing. Take the Instantcert tests again and see how you are doing. If you're getting a lot wrong, go back and use the resources that match your problem section. If you are getting most of the questions right then it's time to sign up for the real thing! Do NOT book early to save a week. Miss the exam and you are out the $97 and waiting 3 months to retake it.
If assembling all of this yourself sounds like a lot, that is the gap our own material fills, and we are biased about it, of course. The InstantCert Biology study guide is 880 flashcards mapped to these same three categories, and 1,046 students have submitted their scores through it. 954 of them passed, about 91%, against a national pass rate closer to 60%.
Happy testing!