Overview
Short answer: take Physics if you genuinely enjoy maths and problem solving — or if you are heading toward engineering, physics, or a maths-heavy science. Take Chemistry if you like a blend of calculation and descriptive content, or if your degree plans point toward medicine, pharmacy, or chemical engineering. Both are IB Group 4 sciences, both are respected, and neither is a soft option. The right choice depends mostly on two things: how much you enjoy maths, and where you want to end up at university.
Physics vs Chemistry at a glance
Both subjects follow the 2025 IB syllabus, are structured around concepts and themes rather than isolated topics, and are assessed with an individual scientific-investigation internal assessment (IA). Both give you a data booklet in the exam. The differences below are about flavour, not format.
| Physics | Chemistry | |
|---|---|---|
| Maths load | Highest of the sciences — constant algebra and multi-step calculation | Moderate — mole calculations, energetics, equilibrium, pH |
| Content style | Abstract concepts and problem solving | Mix of calculation and descriptive theory |
| Memorisation | Lower — fewer facts, more application | Higher — bonding, trends, organic mechanisms |
| Difficulty | Tough if maths is a weakness; rewarding if it is a strength | Broad — punishes gaps because topics build on each other |
| Best for | Engineering, physics, some computer science | Medicine, pharmacy, chemical engineering, life sciences |
What IB Physics is really like
Physics is the most maths-heavy of the IB sciences. Most of what you do is problem solving: read a scenario, pick the right relationship, rearrange it, substitute values, and carry units through to a sensible answer. You will rearrange equations constantly, work in standard form, and often chain several steps together before you reach a result.
The concepts are abstract. You are asked to reason about things you cannot see directly — forces and fields, wave behaviour, energy transfers, and at HL, quantum ideas and relativity. There are fewer facts to memorise than in Chemistry, but "fewer facts" does not mean "less demanding." The challenge is applying a small toolkit of ideas to unfamiliar situations under time pressure. If you like the feeling of cracking a problem, Physics is satisfying. If maths already stresses you, it will stress you here too.
Explore the syllabus with the IB Physics SL course or the fuller Physics HL.
What IB Chemistry is really like
Chemistry sits in the middle. It blends calculation with a fair amount of content you have to learn and recall. On the quantitative side you have moles and stoichiometry, energetics, equilibrium, rates, and pH — real calculations, but generally shorter chains of steps than a hard Physics problem.
On the descriptive side you need to understand and remember bonding and structure, periodic trends, and — a big one — organic chemistry, where you learn families of reactions and the mechanisms that connect them. Topics build on each other: if your understanding of bonding is shaky, energetics and organic will feel harder than they should. Chemistry rewards students who are comfortable switching between "calculate this" and "explain why this happens."
Start with the IB Chemistry SL course, or go deeper with Chemistry HL.
The maths factor — how much you need for each
For the IB Diploma Programme, this is the single biggest deciding factor for most students.
- Physics leans on maths in almost every topic. Algebraic rearrangement, proportional reasoning, working with graphs and gradients, and multi-step calculation are the daily reality. Students who take (and enjoy) a stronger maths course usually find Physics far more comfortable.
- Chemistry uses maths in defined pockets — stoichiometry, energetics, equilibrium, pH — rather than everywhere. The arithmetic is real but usually more contained, and plenty of Chemistry is qualitative reasoning rather than calculation.
If maths is a subject you actively enjoy, that points toward Physics. If you are competent at maths but would rather not have it front and centre in every lesson, Chemistry gives you more variety.
Difficulty — is one harder?
For the IB Diploma Programme, honestly, neither is universally harder — they are hard in different ways, and "which is harder" depends on the student.
Physics is harder if maths and abstract reasoning are not your strengths, because there is nowhere to hide from the problem solving. Chemistry is harder if you dislike memorising detail or tend to leave gaps, because the content is broad and cumulative — organic chemistry in particular catches out students who try to cram it late.
A useful rule of thumb: Physics concentrates its difficulty in depth (a few ideas applied in demanding ways), while Chemistry spreads its difficulty across breadth (a lot of connected material to keep on top of). Pick the kind of hard you would rather live with for two years.
For university
For the IB Diploma Programme, your degree direction is the other decisive factor, and it can override personal preference.
- Physics (frequently at HL, and often paired with HL Maths) is commonly preferred or required for engineering, physics, and some computer science degrees. If any of those are on your list, HL Physics is often the safer choice.
- Chemistry (frequently at HL) is commonly required for medicine, dentistry, pharmacy, chemical engineering, and many life-science degrees. Medicine in particular very often names Chemistry specifically.
These are general patterns, not guarantees. Always check the exact entry requirements on each university's own course pages, because subject and level requirements vary between institutions and countries. Do this early — before you finalise your options — so you are not forced into a late switch.
Who should pick Physics vs Chemistry
For the IB Diploma Programme, pick Physics if you: - Enjoy maths and want it to stay central - Like solving problems more than memorising facts - Are drawn to how and why things work at a fundamental level - Are aiming for engineering, physics, or maths-heavy computing
Pick Chemistry if you:
- Want a balance of calculation and descriptive content
- Are comfortable learning and recalling detail (including organic)
- Enjoy connecting structure, bonding, and behaviour
- Are aiming for medicine, pharmacy, chemical engineering, or life sciences
Many students who love maths and want a full science load take both — they complement each other well, especially alongside HL Maths.
How to decide
This section covers How to decide — what IB examiners reward most often in past papers and coursework.
- Start with your degree. If a target course names Physics or Chemistry, that mostly settles it. Check real university pages, not rumours.
- Rate your maths honestly. Love it? Physics. Fine with it but prefer variety? Chemistry.
- Ask which "hard" suits you — depth-of-problem-solving (Physics) or breadth-of-content (Chemistry).
- Try a real topic of each before committing, rather than deciding on reputation.
How MarkScheme helps you try both
The best way to choose is to sit inside each subject for an afternoon. MarkScheme lets you do exactly that: work through real lessons in [Physics SL](/ib/courses/physics-sl), [Physics HL](/ib/courses/physics-hl), [Chemistry SL](/ib/courses/chemistry-sl), and [Chemistry HL](/ib/courses/chemistry-hl), then [get an answer marked](/mark) to feel how examiners reward each one. Read the honest breakdowns in [Is IB Physics hard?](/blog/ib-physics-hard) and [Is IB Chemistry hard?](/blog/ib-chemistry-hard), and browse the [IB guides hub](/guides/ib) for the wider picture.
Frequently asked questions
For the IB Diploma Programme, not universally. Physics is harder for students who find maths and abstract reasoning difficult, because problem solving runs through the whole course. Chemistry is harder for students who dislike memorising broad, cumulative content. Match the subject to your own strengths rather than chasing a "harder" label.
Is IB Physics harder than Chemistry?
Which is better for engineering?
Physics — usually at HL and often alongside HL Maths — is the more commonly preferred or required subject for most engineering courses. Chemical engineering is the notable exception, where Chemistry is frequently required too. Always confirm on each university's course page.
Which do I need for medicine?
Chemistry is the science most often required for medicine, and frequently at HL. Some medical schools ask for a second science (often Biology) as well. Physics alone is rarely enough on its own for medicine, so check specific requirements carefully.
Can I take both Physics and Chemistry?
Yes, and many students do. They pair naturally, keep the widest range of degrees open, and reinforce shared skills. Just make sure the combined workload — plus HL Maths if you take it — is realistic alongside your other subjects.
How much maths do I really need for Chemistry?
Enough to be comfortable with mole calculations, energetics, equilibrium, and pH — but the maths comes in defined pockets rather than everywhere. If you are competent but not enthusiastic about maths, Chemistry is usually the gentler fit of the two.