How to Take Notes in a Case Interview

The right way to take case interview notes is a two-column page. One narrow column on the left holds your structure, the tree of branches you built during the pause. One wide column on the right holds your work: numbers, scratch math, and one line per data point as it comes in. Leave space at the bottom for your synthesis before you speak. Skip full sentences everywhere. Write only what you will need to look back at, not a record of everything said in the room.

I read hundreds of candidates' pages over the shoulder during live interviews at McKinsey, and the page told me almost as much as the answer did. A messy page with half-finished trees and scribbled arithmetic reads as a messy mind, even when the final number comes out right. A clean page reads as a clean thinker before you say a word.

Why your notes matter more than you think

Your interviewer cannot see your thinking. They can only see what comes out of your mouth and what lands on your page. If you flip your notepad around at the end of the case (and some interviewers will ask to see it), a page of unlabeled numbers and crossed-out guesses undercuts an otherwise strong performance. A page with clear headers, a visible structure, and work that traces logically from top to bottom does the opposite: it backs up your answer with evidence the interviewer can follow without you narrating every step.

Notes also protect you mid-case. Cases run 25 to 35 minutes and involve juggling a prompt, an issue tree, incoming data, and mental math at the same time. Nobody holds all of that in working memory reliably. Good notes are an external hard drive for your brain, freeing you to think about the next branch instead of straining to remember the last number the interviewer gave you.

The page layout that works

Turn your page sideways or draw one vertical line down it, about a third of the way across. The left third is your structure column. Write your issue tree there once, during the structuring pause, and leave it alone. The right two-thirds is your work column, where every new number, every calculation, and every note from a chart goes as the case unfolds.

This layout matters because it keeps your structure visible the entire case. If you scribble your tree at the top of the page and then bury it under three pages of math, you lose the map you built. Consultants and strong candidates alike keep the tree in view so they can point back to it when they explain where a new piece of data fits. I cover how to build that tree from scratch, without memorizing a framework, in the guide to structuring a case interview.

What to write during the opening

When the interviewer reads the prompt, write down the client, the numbers, and the objective, nothing else. Three or four short lines is enough: who the client is, what they make or sell, the key figures (revenue, timeline, growth rate), and the question you are being asked to answer. Do not try to write the prompt verbatim. You are listening for the skeleton, not transcribing a speech.

This is also where you jot your clarifying questions before you ask them, so you do not forget one mid-sentence. I go through exactly what is worth asking at this stage in what to ask before you build structure.

What to write while you structure

During the pause where you build your tree, write branch labels only: three or four words per box, not full sentences. "Revenue: price vs volume" is enough. You do not need to write "I will look at whether the revenue decline is driven by a change in price or a change in volume," because you are about to say that out loud anyway. The page is a skeleton you talk from, not a script you read from.

Leave visible gaps under each branch. You will come back and fill in sub-branches or notes as the case develops, and a cramped page with no white space forces you to squeeze new information in sideways, which is where pages turn messy fast.

What to write during the math

Every case eventually asks you to calculate something, and this is where notes save you the most. Write the formula first, then plug in numbers, then compute. Do not skip the formula step even when the math looks trivial, because writing it out is what catches a wrong setup before you have committed to a wrong number out loud.

Label your units every time. A number without a unit next to it is a number you will misread thirty seconds later when you glance back at the page. "40M units" and "40M dollars" look identical if you only wrote "40M." That single habit prevents more mid-case errors than any other note-taking fix I have seen.

What to write when data or charts show up

When the interviewer hands you an exhibit or reads off new numbers, write down only the numbers that answer your current branch, not everything on the page. Candidates who try to copy an entire chart onto their notepad run out of time and miss the pattern the chart was built to show. Read the exhibit for thirty seconds, decide what matters for your tree, and write that.

One line, one data point, with a label, is the standard. If the chart shows revenue by region for five years, and your branch is about the last two years only, write the last two years only. You can always look back at the original exhibit for anything else.

Before you synthesize

Before you open your mouth to give the final recommendation, take fifteen to twenty seconds to write three or four words per point in a small box at the bottom of your page: your answer, your top two reasons, and any risk worth naming. This keeps your synthesis structured under pressure, when it is easy to ramble through everything you found instead of leading with the answer.

Common note-taking mistakes I saw as an interviewer

The most common failure is writing too much. Candidates who write full sentences run out of time to think, because their hand is busy transcribing instead of their head being busy analyzing. The second most common failure is the opposite: writing so little that the candidate cannot reconstruct their own logic two minutes later and has to ask the interviewer to repeat numbers already given. Both failures come from the same root cause, not calibrating what actually needs to be on the page versus what can stay in your head. I cover this pattern alongside the other ways candidates lose points in the ten most common case interview mistakes.

A third failure shows up specifically in candidate-led cases, where you are driving the pace yourself: candidates keep the same sparse note style that works for an interviewer-led case, then get lost because nobody is prompting them on what comes next. The two formats reward slightly different note habits, which I break down in interviewer-led versus candidate-led cases.

A one-page notes template

Here is the layout as a checklist you can copy onto a blank page before your next practice case.

Practice this layout on a handful of cases before an interview, so the structure becomes automatic and your hand is not deciding where to write something while your brain should be solving the case. If you are still building comfort with the overall case format, start with what a case interview actually is before layering on note-taking mechanics.

The bottom line

Case interview notes exist to support your thinking, not to record everything that happens in the room. Use a two-column page, write labels instead of sentences, always attach a unit to a number, and leave room to synthesize before you speak. Pair a clean page with a genuinely custom structure for the case and you will look like someone who has done this before, because the page proves it.

Go deeper

Note-taking is one small piece of the CaseMap method I teach candidates end to end, from structuring through math through the final recommendation.

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