IB Science Subjects: The Complete Guide to Group 4, SL vs HL and How to Choose

21st October, 2026 | Abhishek Malani | 15 Min Read
Introduction
Every IB Diploma student has to take at least one science, and for many that decision is harder than it looks. Biology, Chemistry, Physics, Computer Science, Design Technology, Environmental Systems and Societies and Sports, Exercise and Health Science all sit in the same group, yet they differ a great deal in content, workload and the careers they point towards. This guide is a hub for the IB science subjects. It explains what Group 4 contains, how Standard Level (SL) and Higher Level (HL) differ, how the assessment works, how to choose between subjects, what the workload feels like and which combinations make sense, so you can decide with the full picture instead of guessing from a subject name.
A note on this article: The IB revises its subject guides from time to time, and schools differ in which Group 4 subjects they offer and how they timetable them. The details below reflect our understanding of the current guides, so confirm exact paper formats, timings and weightings in the latest subject guide and with your school’s IB coordinator. Workload comments are general; individual experiences vary.
IB Group 4 Science subjects comparison showing SL vs HL, assessment formats, and workload.

What Group 4 Is and Why It Matters

The IB Diploma Programme is built from six subject groups, plus the core. Group 4 is Sciences. Every Diploma student must study at least one Group 4 subject, and many students take two.
  • It counts toward your Diploma: Each subject is graded from 1 to 7, and your sciences contribute to the total alongside your other five subjects and the core.
  • It develops practical and analytical skills: All Group 4 courses involve investigation, data handling and evaluation, not only theory.
  • It shapes university options: Many degrees, especially in medicine, engineering and the natural sciences, ask for particular science subjects at a particular level.
  • It has an internal assessment: In every Group 4 subject you complete an individual investigation that is marked by your teacher and moderated by the IB.
Because a Group 4 choice can affect both your workload and your university options, it is worth making deliberately.
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The Group 4 Subjects at a Glance

The subjects below are the ones most commonly associated with Group 4. Not every school offers all of them, so check your school’s subject list first.
Subject What It Covers Typical Fit
Biology
Living systems from molecules and cells to ecosystems, with strong emphasis on data, experimental design and evaluation
Medicine, life sciences, biotechnology, environmental and health fields
Chemistry
Structure, bonding, energetics, reaction behaviour and the quantitative side of matter
Medicine, chemical and biochemical fields, pharmacy, materials and engineering
Physics
Mechanics, waves, fields, energy and modern physics, with a strong mathematical thread
Engineering, physics, computing, architecture and quantitative fields
Computer Science
Computational thinking, programming, systems and data
Computer science, software, data and technology fields
Design Technology
Design process, innovation, materials and user-centred problem solving
Product design, engineering, architecture and design fields
Environmental Systems and Societies (ESS)
Environmental issues viewed through both science and social perspectives
Environmental science, geography, policy and sustainability fields
Sports, Exercise and Health Science (SEHS)
Human physiology, biomechanics, nutrition and performance
Sports science, physiotherapy, health and fitness fields
A few points are worth knowing.
  • Biology, Chemistry and Physics are the traditional core sciences: They are the most common route into medicine, engineering and pure science degrees.
  • ESS is a bridge subject: It can count toward both Group 3 (Individuals and Societies) and Group 4, and it is offered at Standard Level only. Check how your school handles it.
  • Availability varies: Some schools offer only the three core sciences, while others add Computer Science, Design Technology or SEHS. Newer options may also appear as the IB updates its course list.
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SL vs HL in the IB Sciences

You study three subjects at Higher Level and three at Standard Level (some schools allow a slightly different mix, within IB rules), so your sciences might fall into either category.
  • Teaching hours: HL courses are designed around about 240 teaching hours, while SL courses are designed around about 150.
  • Depth and breadth: HL covers extra topics and goes deeper on shared ones. SL covers the essential material without the extension.
  • Mathematical demand: In Physics and Chemistry especially, HL expects more comfort with algebra and quantitative reasoning.
  • Assessment: HL papers are generally longer and include more demanding questions, though the overall structure is similar to SL.
  • University Relevance: Many programmes, such as medicine and engineering, ask for specific sciences at HL, so check entry requirements before you finalise your levels.
A useful rule of thumb is to take at HL the subjects you are most likely to need for your degree and also most able to sustain. An HL you struggle with throughout can pull your total down more than a well-handled SL.

How Group 4 Is Assessed: Papers and the IA

The sciences use a mix of external exams and an internal assessment. The structure is broadly similar across Biology, Chemistry and Physics, with other Group 4 subjects following their own formats.
Component What It Is Approximate Weighting
External exam papers
Written papers combining multiple-choice questions, data-based questions and structured or extended responses, set and marked by the IB
About 80%
Internal assessment (IA)
An individual scientific investigation designed and carried out by you, marked by your teacher and moderated by the IB
About 20%

The exam papers

  • Paper structure: Papers typically mix multiple-choice questions with data-based and longer written questions, and HL candidates sit longer papers than SL candidates.
  • What is tested: Knowledge of the syllabus, the ability to apply it to unfamiliar situations, and skills with data, graphs and experimental design.
  • Command terms matter: Words such as “describe”, “explain”, “evaluate” and “deduce” signal how much depth a question expects.

The internal assessment

  • What it is: You choose a focused research question, design and run an investigation, analyse the results and evaluate the method.
  • How it is written up: The report is a short, structured piece of writing, and its length and format are set out in the subject guide.
  • Why it matters: It is a substantial share of your grade and is entirely within your control, so strong planning pays off.
  • Common strengths: A clear research question, a method that produces usable data, careful analysis and honest evaluation of limitations.
Exact paper numbers, timings, question types and weightings differ by subject and have changed with recent syllabus updates, so use the subject guide for the final word.

How to Choose Which IB Science to Study

When students ask which IB science to choose, the best answer is usually to start from your goals and then test your fit.
  • Start with your intended degree: Look up the entry requirements for several courses you might apply to. Note which sciences, at which level, appear most often.
  • Check your strengths honestly: Look at your recent results and your comfort with mathematics, memorisation, writing and practical work.
  • Notice what you enjoy: You will spend about two years on each subject, so interest matters. A subject you find engaging is easier to keep up.
  • Think about the style of thinking: Physics leans on mathematical reasoning, Biology on breadth and application, Chemistry on a blend of conceptual and quantitative work. Computer Science is about structured problem solving, and Design Technology about creativity and iteration.
  • Look at your whole six-subject package: Choose sciences that fit alongside your other subjects, particularly your mathematics course.
  • Talk to people: Ask current IB students and teachers what the courses are really like. Try sample lessons or past papers if you can.
If you are unsure, a sensible approach is to draw up two or three candidate combinations, check them against your target courses, and compare them for workload and fit.

Workload: What to Expect

IB science courses are demanding, and they tend to ask for steady work through the two years rather than a last-minute push.
  • Content load: Biology is often described as content-heavy, with a lot to learn and apply. Chemistry and Physics tend to combine concepts with calculation.
  • Practical and IA time: Lab work and the IA take real hours, and they compete with other deadlines such as the Extended Essay and Theory of Knowledge.
  • HL vs SL: An HL science adds a significant number of teaching hours and extra topics, so two HL sciences can be a heavy load.
  • Peaks in the calendar: The IA, mock exams and final papers cluster in particular periods, so plan around them.
  • What helps: Regular revision, practice with past-style questions, early work on the IA and keeping notes organised from the start.
Taking two sciences is manageable for many students, but it works best when your other subjects and commitments leave room for it.

Subject Combinations That Work

There is no single correct pairing, but some combinations match common goals.
  • Medicine and health sciences: Chemistry and Biology, often both at HL, with a mathematics course you can handle. Check each university’s stated requirements.
  • Engineering: Physics, usually at HL, with a strong mathematics course, and sometimes Chemistry or Design Technology as a second science.
  • Computer science and technology: Computer Science alongside a mathematics course suited to the degree, sometimes with Physics.
  • Environmental and sustainability fields: ESS with Biology or Chemistry, and a Group 3 subject such as Geography or Economics.
  • Sports and health fields: SEHS or Biology, often with Chemistry.
  • Architecture and design: Design Technology with Physics and a suitable mathematics course, plus an arts or humanities subject.
  • Undecided: A balanced combination such as one science at HL and one at SL, alongside mathematics, keeps several doors open.
These are illustrations, not rules. The correct combination for you depends on your target universities, so verify their requirements before you commit.

Subject Guides and IA Ideas

This page is the overview. For detail on each subject, use the dedicated pages below.
  • IB Biology: Study guide and IA ideas 
  • IB Chemistry: Study guide and IA ideas
  • IB Physics: Study guide and IA ideas 
  • IB Computer Science: Study guide and IA ideas 
  • IB Design Technology: Study guide and IA ideas 
  • IB Environmental Systems and Societies: Study guide and IA ideas 
  • IB Sports, Exercise and Health Science: Study guide and IA ideas 

Common Mistakes When Choosing a Science

  • Choosing by reputation: Hearing that a subject is easy or hard tells you little about how it will suit you.
  • Ignoring university requirements: Discovering late that a course needs a specific science at HL can force an awkward change.
  • Overloading on HL: Taking too many demanding HL subjects can hurt your results across the board.
  • Underestimating the maths: Physics and Chemistry in particular reward comfort with mathematics. Match your science choices to your maths course.
  • Following friends: Picking a subject because a friend did is rarely a good reason.
  • Leaving the IA late: The internal assessment needs early planning, and rushing it costs marks.
  • Not asking about school options: Schools differ in what they offer and in how they combine subjects, so check what is available before you plan.

How Quest for Success Can Help

Choosing sciences is one of the biggest decisions in the IB, and it connects to your target universities, your maths course and your workload. At Quest for Success, we help students compare Group 4 options against their goals, sketch out sensible subject combinations and plan their time across papers, the IA and other commitments. If you would like a second opinion on a combination you are considering, share your target courses and current subjects and we will work through it with you.

Summary

Group 4 contains the IB sciences: Biology, Chemistry, Physics, Computer Science, Design Technology, Environmental Systems and Societies and Sports, Exercise and Health Science, though schools offer different selections. Each is available at SL or HL, with HL adding teaching hours, depth and demand. Assessment combines external exam papers, about 80% of the grade, with an internal investigation, about 20%, though details vary by subject. To choose, start from your intended degree, check your strengths and interests, think about your whole subject package and consider your workload. Common combinations point towards medicine, engineering, computing, environmental or design fields, but the right pairing depends on your own goals and the requirements of your target universities.
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Explore More IB Resources

Transitioning to the IB Diploma Programme can be challenging, especially when adapting to new subjects, assessment methods, and academic expectations. Explore these guides to understand the transition process and prepare for the next stage of your IB journey.
  • IB Study Plan : Build an Effective Revision Strategy – Learn how to organise your study schedule, prioritise subjects, manage revision time, and balance your academic workload throughout the IB Diploma Programme.
  • IB Grade Boundaries : Understand Scores and Grade Requirements – Understand how IB grade boundaries help determine final subject grades and learn why knowing the scoring requirements can support more focused exam preparation.
  • IB MYP to DP Transition Guide : Understand the key differences between the Middle Years Programme (MYP) and Diploma Programme (DP), including subject choices, academic expectations, and preparation strategies.
  • IGCSE to IB Transition Guide : Discover how the IB differs from IGCSE, what to expect from its learning and assessment styles, and how to prepare for a smooth transition.

FAQs

The IB sciences sit in Group 4. They include Biology, Chemistry, Physics, Computer Science, Design Technology, Environmental Systems and Societies and Sports, Exercise and Health Science. Your school may offer only some of these.

Yes, Every Diploma student studies at least one Group 4 subject. Some students take two, and a few take more, depending on their school and goals.

Start with your intended degree and its entry requirements, then consider your strengths, interests and workload. Compare two or three candidate combinations and talk to teachers and current students.

HL courses have more teaching hours, cover additional topics and go deeper, while SL courses cover the essential material. HL papers are generally longer and more demanding.

Through external exam papers and an internal assessment, an individual investigation marked by your teacher and moderated by the IB. Papers account for the larger share of the grade, but exact formats and weightings vary by subject, so check the subject guide.

Many students do, It works best when your other subjects and commitments leave room for the extra workload. Check how your school allows the combination.

Medicine pathways commonly ask for Chemistry and often Biology, frequently at HL. Engineering pathways commonly ask for Physics and a strong mathematics course. Requirements differ by university, so check each one directly.

Not sure which sciences suit you? Reach out to Quest for Success; we are here to help you choose with confidence.

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