Overview
For the IB Diploma Programme, short answer: choose Biology if you'd rather learn and recall a large amount of detailed, real-world content than crunch numbers, and choose Physics if you enjoy maths, problem-solving, and abstract ideas more than memorising. These two sit at opposite ends of the science spectrum, so the decision really comes down to one honest question — memory or maths? The rest of this guide unpacks both so you can pick on fit, not on reputation.
Both are Group 4 sciences on the 2025 concept- and theme-based syllabus, and both are assessed with written papers plus an individual scientific investigation for the internal assessment. That shared frame hides a big difference: the kind of thinking each subject rewards day to day is almost the mirror image of the other.
Biology vs Physics at a glance
For the IB Diploma Programme, use the table as a map, not a verdict — the sections below explain what each course actually feels like.
| Biology | Physics | |
|---|---|---|
| Content style | Systems, processes, detailed recall | Concepts, calculations, derivations |
| Maths load | Lowest of the sciences — data and basic stats | Highest — algebra, multi-step problems |
| Memorisation | Large volume of precise terminology | Light — core equations and definitions |
| Difficulty | Demanding volume, point-per-mark precision | Demanding maths and abstract concepts |
| Best for | Detail-lovers, future medics and life scientists | Problem-solvers, future engineers and physicists |
What IB Biology is really like
For the IB Diploma Programme, biology is the least maths-heavy science in the diploma. You'll handle data, graphs, and some statistics, but nothing approaching Physics's calculation density. The real challenge is volume. You move through cells, molecular biology, genetics, physiology, ecology, and evolution, and every area brings its own large vocabulary of precise terms and processes you must recall accurately.
Biology exam answers are usually marked point per mark: each distinct, valid point earns a mark, and examiners look for specific correct statements. A vague, hedged, or slightly-wrong term simply scores zero. That makes success a matter of disciplined, cumulative revision rather than last-minute cramming — there is far too much to hold together if you leave it late. Students who genuinely enjoy understanding how living systems fit together, and who are willing to be meticulous, tend to do well.
Preview the scope in the IB Biology SL course or step up to Biology HL.
What IB Physics is really like
For the IB Diploma Programme, physics is the most maths-heavy science. From the start you work with algebraic rearrangement and multi-step problem solving, and the difficulty builds as you meet increasingly abstract concepts — fields, waves, and, especially at HL, quantum physics and relativity. You can't picture much of this directly; you have to reason about it through equations and models.
The memorisation load is comparatively light: a manageable set of core equations, constants, and definitions. What Physics asks instead is that you apply them — rearrange, substitute, chain several steps together, keep your units straight, and arrive at a justified answer to an unfamiliar problem. Marks reward correct working and sound physical reasoning, not recall of long lists. If a problem clicking into place is satisfying to you, Physics is rewarding. If maths makes you anxious, it can feel relentless.
Explore it through the IB Physics SL course or Physics HL.
The memory-vs-maths trade-off
For the IB Diploma Programme, this is the core decision, and it's cleaner than most students expect.
- Biology asks you to remember — accurately, and a lot. The maths is light, but the sheer quantity of content and the precision demanded by point-per-mark answers is where students lose grades.
- Physics asks you to calculate and reason. The recall load is small; the hard part is applying concepts, doing multi-step maths correctly under time pressure, and staying confident with abstraction.
Ask yourself honestly: would you rather sit down to a page of questions that reward remembering the exact right terms, or to a set of problems you have to work through with algebra? Your gut answer is a strong signal — and it usually points one way quite clearly for these two subjects.
Difficulty — is one harder?
For the IB Diploma Programme, physics carries the harder reputation, and there's truth to it: the maths and abstraction defeat students who chose it without enjoying either. But "harder" depends entirely on the person. Biology's volume trips up plenty of capable students who underestimate it and revise too late, then can't recall enough precise detail when it counts.
We won't quote grade statistics here, because outcomes vary by cohort, school, and effort, and headline averages rarely reflect your situation. The honest framing is this: Physics is hard if maths and abstraction aren't your strengths; Biology is hard if sustained, precise memorisation isn't. Neither is a soft option, and neither is easy for the wrong kind of thinker.
For a deeper look at each, see Is IB Biology hard? and Is IB Physics hard?.
For university
For the IB Diploma Programme, your degree plans can settle this decision quickly, so check them early.
Biology — often at HL — is commonly required or preferred for medicine, dentistry, veterinary science, and the biosciences, frequently alongside Chemistry. If a health or life-science degree is your direction, Biology is usually the science that keeps those doors open.
Physics — often at HL, and usually with HL Maths — is preferred or required for engineering, physics, and some computer-science degrees. If you're aiming at a technical or physical-science route, Physics is typically the one that matters.
Requirements differ between countries and between individual universities, so treat this as guidance, not gospel — check the specific offers for every course on your list before you lock in your subjects. And a quick reality check: neither subject substitutes for the other in these pathways, so let the degree, not the reputation, guide you.
Who should pick Biology vs Physics
For the IB Diploma Programme, lean Biology if you: - Prefer detailed, real-world systems over calculations - Want the lightest maths load of the sciences - Are comfortable committing to steady, high-volume, precise revision - Are drawn to medicine, dentistry, veterinary, or the wider life and health sciences
Lean Physics if you:
- Enjoy problem-solving and are comfortable (or actively happy) with maths
- Cope well with abstract, conceptual ideas
- Would rather understand a few principles deeply than memorise long lists
- Are targeting engineering, physics, or a maths-heavy degree — and can pair it with HL Maths
If your school allows it and you fit both profiles, taking two sciences is a common and sensible choice.
How to decide
This section covers How to decide — what IB examiners reward most often in past papers and coursework.
- Rate your maths comfort honestly. If numbers and algebra drain you, Physics will be a grind; if precise memorisation drains you, Biology will.
- Check your degree plans. Look up real requirements for 2–3 target courses. Medicine tends to point to Biology (with Chemistry); engineering and physics tend to point to Physics (with HL Maths).
- Try a topic of each. Nothing beats sitting with real material and noticing which one you'd rather keep doing.
- Talk to your teachers. They know your working style and how each course runs at your school.
How MarkScheme helps you try both
You don't have to guess. MarkScheme hosts free, full courses for [Biology SL](/ib/courses/biology-sl), [Biology HL](/ib/courses/biology-hl), [Physics SL](/ib/courses/physics-sl), and [Physics HL](/ib/courses/physics-hl), so you can work through a real topic in each before committing. When you write a response, you can [get an answer marked](/mark) against examiner-style criteria to feel how differently the two reward you — the point-per-mark precision of Biology versus the multi-step problem logic of Physics. Browse everything from the [IB guides hub](/guides/ib).
Frequently asked questions
This section covers Frequently asked questions — what IB examiners reward most often in past papers and coursework.
Is IB Physics harder than Biology?
Physics has the harder reputation because of its maths and abstract concepts, and for maths-averse students it usually is tougher. But Biology's enormous content volume and point-per-mark precision defeat plenty of students too. "Harder" depends on your strengths, not on the subject alone.
Which science is easier, Biology or Physics?
There's no honest universal answer. Biology is lighter on maths but heavy on memorisation; Physics is lighter on memorisation but heavy on maths and abstraction. The easier one for you is whichever plays to your strengths — so judge by the kind of thinking each demands, not by reputation.
Which has more maths, Biology or Physics?
Physics, clearly. It's the most maths-heavy science, built on algebra, multi-step problem solving, and derivations. Biology has the lightest maths of the sciences — mostly data handling and basic statistics.
Do I need Biology or Physics for medicine?
Medicine, dentistry, and veterinary courses usually point to Biology, often at HL and frequently alongside Chemistry, rather than Physics. Requirements vary by university and country, so check each course's specific offer before deciding.
Can I take both Biology and Physics in the IB?
Yes, and some students do. Because they exercise very different skills, the combination can be demanding, but if your timetable allows it and you can manage the workload it keeps a wide range of degrees open.