IB mark schemes explained: marking points, M1 A1 marks, markbands and how to self-mark

An IB mark scheme (the IB writes it as one word, markscheme) is the list of what earns each mark on a paper. In science short answers, most marks are one valid point each, and the markscheme lists more acceptable points than there are marks. In maths, marks are split into method (M), accuracy (A) and reasoning (R) marks, with follow-through so one early slip doesn't wipe out every later part. Essays and long written answers are marked against markbands: level descriptions where the examiner picks the best fit.

Once you can read a markscheme the way an examiner does, you can mark your own past papers honestly and, more usefully, see exactly what a full-mark answer contains. Every example below is invented for this guide; real markscheme wording belongs to the IB and isn't reproduced here.

How are marks awarded in IB science answers?

In Biology, Chemistry and ESS short answers, a markscheme is a list of marking points. Each point is worth one mark, and a 3-mark question often lists five or six acceptable points with a note such as max 3. The examiner ticks each point your answer makes clearly, then stops at the maximum. The order you make them in rarely matters; what matters is that each one is there, stated precisely enough.

Markschemes use a small set of conventions. You'll meet these most often:

A science example: one point per mark

Question (2 marks): Explain why increasing the temperature increases the rate of a reaction.

Illustrative markscheme (max 2):

• particles have a higher average kinetic energy / move faster;
• a greater proportion of collisions have energy greater than or equal to the activation energy;
• collisions are more frequent / there are more collisions per unit time.

Note: do not accept "more collisions" without reference to time or frequency.

The first answer earns the energy point and nothing else. "More collisions" is exactly the vague phrase the note rules out: a reaction that runs for longer also has more collisions. The second answer reaches full marks on the energy and activation-energy points alone; it would not need the frequency point even if it left out "per second". That is how point-based marking works: two clear points beat four vague ones.

Error carried forward in calculations

Error carried forward (ECF) means one mistake is penalised once. If you get an early part of a calculation wrong and then use your wrong value correctly in a later part, the examiner can award the later marks as if your value had been right. Maths markschemes apply the same idea under the name follow-through (FT, below).

Invented example: 25.0 cm³ of sodium carbonate solution reacts with 21.40 cm³ of 0.100 mol dm⁻³ HCl. Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂.

The student loses one mark, not three. ECF has limits, though. The markscheme says where it applies, and it isn't available on every part. If your error makes a later step much simpler, or leads to an impossible result, the later marks may not be given. And the examiner can only follow your error forward if they can see it: had the student written only "0.0856" in part (c), nobody could tell the method was right, and that mark would go too.

How do M1, A1, R1 and AG marks work in IB maths?

Maths AA and AI markschemes label every mark by type. In our words:

On calculator papers the IB accepts either the exact value or an answer correct to three significant figures, so give 3 s.f. unless the question says otherwise. And a correct answer with no working is a gamble: it may earn every mark on a short question, but where the M marks are the point of the question, as in any "show that", it earns little or nothing.

A maths example: method, accuracy, reasoning and follow-through

Question: The first two terms of a geometric sequence are 48 and 36.

Now take a student who writes r = 0.72 in part (a). They divided the right way round, so they keep M1 but lose A1. In part (b), 0.72 < 1 earns R1, 48 ÷ (1 − 0.72) earns M1, and their answer of 171 (from 171.43) earns A1 as follow-through. One slip, one mark lost, not four.

Part (c) shows why AG parts matter. You can't earn anything by writing 192(1 − 0.75ⁿ) at the end; the marks are for the substitution and the simplification. But the printed answer is also a free check: a student with r = 0.72 who reaches (c) can see something is off. And part (d) can be done using the given result even by someone who couldn't prove it. Since 0.75¹⁵ ≈ 0.0134 gives S₁₅ ≈ 189.4, and 0.75¹⁶ ≈ 0.0100 gives S₁₆ ≈ 190.1, the answer is 16. Never skip the part after a "show that" just because the "show that" beat you.

How do markbands work for essays and extended responses?

Where quality of argument matters more than a list of facts, the IB uses markbands (level descriptors) instead of, or alongside, marking points. In ESS Paper 2, for example, the last part of each 20-mark Section B essay (9 of the 20 marks) is marked with bands of 1–3, 4–6 and 7–9, while the earlier parts use a point-based markscheme. The Extended Essay, TOK and the internal assessments use criteria with bands too, as do the essay-style questions in subjects such as Psychology and Global Politics; your subject guide sets out the exact bands.

Examiners apply bands by best fit. They read the whole response, decide which level description fits it best, then place it high or low in that band depending on how fully it meets the description. A response doesn't need to tick every phrase in a band to reach it, and the top band doesn't demand perfection: the IB's Extended Essay guide says so explicitly, and markbands generally work that way.

Here is an invented example of how levels step up for a 9-mark "evaluate" answer. It isn't IB wording, but the progression is typical:

Notice what separates the bands: not length, but whether you weigh both sides, use specific evidence and reach a supported judgement. That maps directly onto the command term, which is why knowing what each command term asks for matters most in banded questions.

How do you mark your own paper with a markscheme?

1. Finish the whole paper first, timed, without peeking. Marking as you go turns a test into a reading exercise.
2. Mark in a different colour, one marking point at a time. For each point, find the sentence in your answer that makes it. If you have to explain to yourself what you "meant", it doesn't count. The examiner can only credit what is on the page.
3. Apply the notes and the max. Read every "do not accept" note: they exist because those wordings are common. Cap each part at its maximum, even if you made more valid points.
4. In maths, mark method separately from answer. Give yourself M marks for valid methods even if the result is wrong, use follow-through honestly, and give no A marks after a wrong method.
5. For banded answers, choose the band, then write one sentence on why it isn't the band above. If you can't name what's missing, ask your teacher to mark that answer.
6. Log every lost mark with its cause: missing knowledge, wrong command term, vague wording, calculation slip, or time. The past papers guide has an error-log layout.

It's easy to be generous with yourself, especially on vague answers. Every so often, swap papers with a friend and compare the marks you each gave: the differences show you where your self-marking is soft.

How can you use markschemes to revise, not just to mark?

A markscheme is the most concentrated description of a full-mark answer you'll find. Use it to build what you write, not only to score it.

Build answer templates for repeated question types

The same question shapes come back with different content. Collect the markschemes for one shape and write the scaffold they share. For "explain the effect of temperature (or concentration, or surface area) on rate", it's: what changes about the particles → what that does to collision frequency or energy → the link to activation energy → therefore the rate. For a "show that" in maths: start from a formula or definition, substitute, simplify one visible step at a time, end on the printed result. Then fill it with new content.

Collect the keywords that carry marks

Some marking points hinge on a single term. Keep a page per topic of the phrases that keep appearing as required: complementary shape, active site, denatured and hydrogen bonds in Biology; per unit time, proportion of particles with energy ≥ E_a and electrostatic attraction in Chemistry. The vague versions next to them (killed, more collisions, it reacts faster) are just as useful to write down, because they're the ones you'll reach for under pressure. These make good flashcards.

Calibrate length by counting points

A 3-mark "explain" needs three distinct, creditable points; a 1-mark "state" needs one. Before you write, count the marks and plan that many points. It also stops you writing a page for a 2-mark question.

Read the subject report

After each session, examiners write a subject report on how candidates did, including the answers that commonly lost marks. They sit on the IB's resource centre for schools, so ask your teacher for the recent ones in your subject. They're the closest thing to an examiner telling you what they wanted.

What can't a markscheme tell you?

• It isn't a complete list of right answers. Markschemes are written for trained examiners, who credit valid answers that aren't listed. If your answer is correct but missing from the scheme, ask your teacher rather than marking it wrong.
• It shows one method, not the only one. In maths especially, a different valid method earns the same marks.
• Memorised phrases break when the question changes. If you learn a markscheme answer word for word, a question that twists the context exposes it. Learn why each point earns a mark.
• Old markschemes follow old syllabuses. Biology and Chemistry changed for exams from 2025, ESS and Global Politics for 2026, and Psychology for 2027, so check that a point is still on your course before you learn it.
• Your total isn't a grade. Raw marks only become a 1–7 after grade boundaries are set each session. Why you can't turn one paper's score into a predicted grade explains the catch.