IB Maths papers are marked point by point. Each question is split into small marks: M marks for a correct method, A marks for correct answers and values, R marks for reasons, and AG where the answer is printed in the question, so only the working counts. Your score on a question is the number of those points you showed on the page, which is why good working can earn most of the marks even when the final answer is wrong.
This post explains the codes you will see in an IB markscheme and then marks one question line by line. The mark split in the example is my own illustration in the IB style, not taken from an IB markscheme.
The codes in one table
| Code | What it rewards |
|---|---|
| M1 | A correct method, applied to the right numbers, even if a slip follows. |
| A1 | A correct answer or value. It normally needs the M mark before it. |
| R1 | A clear reason or justification: the "because" in your answer. |
| AG | Answer given. The result is printed, so the marks are for the steps. |
| FT | Follow through. A later mark can be earned using your own earlier wrong answer, used correctly. |
| (M1), (A1) | Marks in brackets can be implied by later correct work, even if that step is not written down. |
Our mark scheme codes guide covers each of these, and the codes other boards use, with a short example of the mark being gained and lost.
One question, marked line by line
Example · Paper 1 style · 8 marks
Let $f(x) = x^3 - 6x^2 + 9x + 1$.
(a) Find the coordinates of the stationary points of the graph of $f$. [5]
(b) Use the second derivative to determine the nature of each stationary point. [3]
Solution
(a)
$f'(x) = 3x^2 - 12x + 9$ A1
$3x^2 - 12x + 9 = 0$ M1
$3(x - 1)(x - 3) = 0$, so $x = 1$ or $x = 3$ A1
$f(1) = 1 - 6 + 9 + 1 = 5$ and $f(3) = 27 - 54 + 27 + 1 = 1$
Stationary points $(1, 5)$ and $(3, 1)$ A1 A1
(b)
$f''(x) = 6x - 12$ A1
$f''(1) = -6 < 0$, so $(1, 5)$ is a maximum R1
$f''(3) = 6 > 0$, so $(3, 1)$ is a minimum R1
Notice what each mark is attached to. The M1 is for setting the derivative equal to zero, which is the method. The R1 marks are for the inequality and the conclusion together: "$f''(1) = -6$, maximum" states a value and a verdict but never gives the reason that links them.
Three students, three scores
Student A writes everything above and scores 8.
Student B makes one slip: $f(1) = 1 - 6 + 9 + 1 = 3$. They lose one A1 in part (a), because the point $(1, 3)$ is wrong. In part (b), the reasoning still holds: the second derivative at $x = 1$ is still negative, so the R1 marks are still there. If a later part used the maximum value, follow-through would let them earn it with their $3$, as long as they used it correctly. One slip costs one mark, not five.
Student C writes only "$(1, 5)$ maximum, $(3, 1)$ minimum". The answers are right, but the question asks for the second derivative to be used, and there is no derivative, no equation and no reason on the page. Some answer marks can be implied by correct work, which is what brackets in a markscheme mean. A method you were told to use cannot be implied by an answer you could have got another way, so this student could lose most of the 8 marks.
The difference between B and C is the whole point of working. B made a mistake and kept 7 marks. C made no mistake and could have lost most of them.
AG: when the answer is in the question
When a question says "show that", the markscheme writes AG next to the final line. That line earns nothing by itself; the M and A marks are on the steps before it.
Example · AG · 3 marks
Show that the area enclosed by $y = 2x + 1$, the $x$-axis and the lines $x = 0$ and $x = 2$ is $6$.
Solution
$\displaystyle \text{Area} = \int_0^2 (2x + 1)\,dx$ M1
$= \left[x^2 + x\right]_0^2$ A1
$= (4 + 2) - 0$ A1
$= 6$ AG
Writing "area $= 6$ as required" with nothing before it scores 0. Writing the integral and the antiderivative, and then making a slip, still earns the M1.
Follow-through has limits
FT means you lose a mark once, not over and over. Between parts of a question, IB markschemes commonly allow follow-through when your working is shown. Within the same part, later accuracy marks that use a wrong value are usually lost. And FT never rescues a method that was wrong: it only credits correct work done on your own earlier answer.
So the practical rule is simple: if you get an answer you suspect is wrong, use it anyway in the next part and keep going. Leaving the next part blank is the only way to make sure you get nothing for it.
Accuracy marks and rounding
On calculator papers, A marks can be lost to rounding. Give final answers exactly or to 3 significant figures unless the question says otherwise, and keep full calculator values until the last line. Rounding a value early and carrying it forward can change the final answer at 3 significant figures, which costs an A mark even though the method was perfect.
What this means for how you write
- Write the method line before you calculate. The equation you are solving, the integral you are finding, the distribution you are using. That line usually carries the M mark.
- Give reasons in words. "Since $f''(1) < 0$" or "since $\log$ of a negative number is undefined". R marks need the reason, not just the conclusion.
- Never skip to a printed answer. For AG, every step is the answer.
- Keep going after a slip. Follow-through only works if there is a later part to follow through into.
Mark your own work like this
When you mark practice papers, do not just tick the final answer. Write M1, A1 or R1 next to each line that earns one, and circle the first line where a mark was lost. Within a week you will see the pattern: lost method marks mean revising a topic, lost accuracy marks mean slowing down, and lost R marks mean writing one more sentence.
To try it, pick a set from the AA SL questions on applications of differentiation; each comes with a step-by-step mark scheme. A free account (no card) adds 5 more practice questions on every topic with instant feedback, full worked answers on free questions, and your streak and progress on any device. Create a free account to keep a record of the marks you lose and why.
Practise this topic
FAQ
What does M1 A1 mean in IB Maths?
M1 is a method mark, for a correct method applied to the right numbers. A1 is an accuracy mark, for a correct answer or value. An A mark normally depends on the M mark before it, so a correct answer from a wrong method does not earn it.
What is an R1 mark in IB Maths?
A reasoning mark, given for a clear reason or justification. For example, stating that the second derivative is negative, so the point is a maximum.
What does AG mean in an IB markscheme?
Answer given. The answer is printed in the question, so writing it down earns nothing. The marks are for the working that leads to it.
Every code (M, A, R, AG, FT, brackets and more) in plain English, each with a short example of the mark being gained and lost.
Read the full mark scheme codes guide →