Reading a markscheme
What M1, A1, R1, AG and follow-through mean, how science and essay markschemes work, and a table of markscheme phrases with what to write.
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Why read markschemes at all
A markscheme is the examiner's instructions: which points earn marks, which answers are accepted, and what to do when a student goes wrong part way. Reading them teaches you what a mark looks like in your subject, which is often less than you'd write and more precise.
Markschemes differ by subject. Math uses letter codes for each mark. Sciences list marking points. Essay subjects use markbands. This chapter covers all three.
Math mark codes
Math markschemes for both courses (analysis and approaches, and applications and interpretation) give every mark a letter and a number. M1 is one method mark; A2 is two accuracy marks.
| Code | Stands for | Awarded for |
|---|---|---|
| M | Method | Attempting to use a correct method, such as substituting into the right formula |
| A | Answer or accuracy | A correct answer or a correct step. Usually depends on the M mark before it |
| R | Reasoning | Clear reasoning, such as a justification or an explanation of why a step holds |
| AG | Answer given | The line where the answer printed in the question appears. It earns no marks itself |
| FT | Follow through | Correct work that uses your own earlier wrong answer |
A few rules decide how these combine.
A marks depend on M marks
An accuracy mark usually needs the method mark before it. You can't normally score M0 A1: a right answer from a wrong method gets nothing. So a correct final answer doesn't automatically get full marks; examiners check the working.
When M1A1 sits on one line, the M1 is usually for the right method (substituting into a formula, say) and the A1 for doing it with the right values.
Marks in brackets are implied
A mark in brackets, such as (M1), can be awarded without that step being written down, if correct later work shows you must have done it. Marks without brackets need the work to be seen. This is why a bare answer can sometimes score full marks and sometimes score only the last mark.
Follow through
If you get part (a) wrong and use that wrong value correctly in part (b), you can still earn the marks in (b). The markscheme writes "their" to mean your value, as in "their answer to (a)".
Follow through has limits:
- within one part, once you make an error, later accuracy marks that use it are lost, though method marks can still be earned;
- if your error makes the rest of the question much easier, fewer marks are given;
- if your error leads to an impossible value, such as a probability greater than 1, the final answer mark is lost;
- after a "show that" you didn't manage, use the value given in the question, not your own.
Other rules worth knowing
- Hence: if the question says "hence" and not "hence or otherwise", other methods aren't allowed.
- Alternative methods: whole-question alternatives appear as METHOD 1, METHOD 2; alternatives for a part appear as EITHER and OR. Other correct methods are marked in line with these.
- Equivalent forms are accepted unless the question asks for a particular form. Calculator notation, such as 2.3E4, is not.
- Accuracy: unless the question says otherwise, answers must be exact or correct to three significant figures.
- Misreading a value from the question costs one mark, once, if the rest of the work is correct.
- Further working: once a correct answer is written, later working is ignored, unless you then use a wrong value from it.
Science markschemes
The sciences list the separate points that earn marks, one per line. Physics and chemistry put a tick (✔) at the end of each marking point; biology uses a semicolon. A question worth 3 marks might list five points, with max in the total column: any three of them score.
Inside the points:
- a slash (/) separates alternative words that both earn the mark, and OR separates alternative answers;
- words in chevrons « » (physics and chemistry) or brackets (biology) help the answer read but aren't needed for the mark;
- underlined words must appear;
- OWTTE, "or words to that effect", means any wording with the same meaning scores;
- ECF, "error carried forward", means a wrong earlier answer used correctly later still earns those later marks. "Do not allow ECF" turns that off.
The notes column then says what else to accept:
- Award [2] for correct final answer: the right answer alone gets full marks, working or not;
- Award [1 max] for: a partial answer can't get more than one mark;
- Accept lists other answers that score, and Do not accept lists common answers that don't;
- Ignore names things that neither gain nor lose marks, such as missing state symbols in some chemistry answers.
Units and significant figures aren't penalized unless the markscheme says so. Physics also gives full marks to a correct answer with no working, unless the markscheme says otherwise. Don't rely on that: with working shown, a slip can still earn method marks.
Essay subjects and markbands
Essays and extended answers, in economics, history or English for example, are marked with markbands: levels of performance for each criterion, each covering a range of marks.
The examiner reads the whole answer and picks the band that describes it best, then places the mark within the band. That is called best fit. An answer doesn't have to meet every line of a band to reach it, and the top band doesn't mean a perfect answer.
So for essays, a markscheme tells you less about the right answer and more about the qualities being rewarded: the analysis, the use of evidence, the structure of the argument. Read the descriptors for the top two bands and ask which words in them your answer shows.
Markscheme phrases, and what to write
| In the markscheme | What it means | What to write |
|---|---|---|
| M1 | A mark for using a correct method | Show the method: the formula and what you put into it |
| A1 | A mark for a correct answer or step, usually after an M mark | The answer, given the method was right and shown |
| (M1), (A1) | A mark that can be implied by later correct work | Write the step anyway; it's the only safety if your answer is wrong |
| R1 | A mark for reasoning | A sentence that says why: "since the gradient is positive…" |
| AG | The answer printed in the question; no marks of its own | Every step before it, then the given result |
| FT, "their" | Marks for correct work using your own wrong value | Carry on with your value and keep showing the method |
| ✔ or ; | One marking point | One clear point per mark available |
| max | More points listed than marks | Enough distinct points to cover the marks, not every one |
| / | Either word scores | Either word |
| « » or ( ) | Not needed for the mark | Optional, but it helps the answer read |
| Underlined word | Must appear | That exact word or term |
| OWTTE | Any wording with the same meaning | Your own words, if the meaning is exact |
| ECF | Error carried forward | Use your earlier answer and keep going |
| Accept | Other answers that also score | Any of them |
| Do not accept | Common answers that score nothing | Not these, even if they feel close |
| Award [n] for correct final answer | The answer alone gets full marks | The answer, with working in case it's wrong |
| Award [1 max] | A capped mark for a partial answer | The full answer, to get past the cap |
| Ignore | Neither gains nor loses marks | Nothing special |
Marking yourself honestly
When you mark your own answer, mark it as an examiner would, not as you meant it:
- Give yourself a mark only where your working shows it. "I knew that" isn't on the page.
- If the markscheme names a term or a unit, check you wrote it.
- If you got the method right and the answer wrong, give the method marks and not the answer marks. That's exactly the information you need: the method is fine, the slip is not.
The question bank puts the markscheme beside every question; you reveal it, compare, and mark yourself: got it right or got it wrong.
Sources
IB markschemes are sold with past papers through the IB's official store, and specimen papers are available to teachers through the IB. We describe the notation in our own words, from the instructions printed in recent markschemes (2021 to 2025 for math, May 2025 for the sciences).
- International Baccalaureate. Assessment and exams, Diploma Programme.
- International Baccalaureate. Physics guide, first assessment 2025: on buying past papers and markschemes from the IB store.
- International Baccalaureate. Extended essay guide: best-fit approach and markbands.
- International Baccalaureate. Mathematics: analysis and approaches and Mathematics: applications and interpretation markschemes, "Instructions to examiners", May 2021 to November 2025.
- International Baccalaureate. Biology, Chemistry and Physics Paper 2 markschemes, May 2025.