Are you preparing for a case interview and feeling unsure about the math part? You're not alone. Many candidates struggle with doing calculations under time pressure. Often, the issue isn’t your ability – it’s a lack of confidence.
In this article, Coach Mariana explains why case math can be so challenging, what really matters, and how you can build confidence step by step. You'll learn how to target your weak spots with the right exercises, avoid common mistakes in thinking, and stay calm when nerves start to take over during the interview.
One of these days I entered a PrepLounge question and found this answer posted by a coach about how one could go from good to great in an interview:
"(...) I spent many years as an interviewer at MBB, and in my experience, what really sets candidates apart is the level of confidence they project and the way they engage the “client” – in this case, the interviewer. Ultimately, the question your interviewer is asking themselves is: Does this person have what it takes to become a partner and manage clients independently?(...)”
I thought to myself: that's exactly it. Why do some candidates make it through even making some mistakes during case interviews while others do everything by the book and don't get an offer? More often than not, the reason lies in the subtle things related to case interviews, such as projecting confidence. People make mistakes and real-life projects may sometimes get messy. Being able to stay composed and convey confidence to the clients, so that they have the sense that everything is under control despite a setback, is crucial.
Math abilities are a recurrent issue candidates face, and it often kills their confidence during case interviews. The root cause of this issue may be different depending on the person. Let's break it down into two types of people: the “I am not a numbers person” and “I have a quant background and I still don't get it".
Starting with the first one, the person that doesn't think math is their thing, usually the problem is in one of two areas. Either they lack experience because they never had much interest in the subject but do not necessarily have bad feelings about it. Or they had bad experiences in this field, like a really tough math teacher or some difficult professional projects they got involved in, and for that reason they avoid topics related to quantitative work.
The second type is the one who is actually familiar with math and sometimes even good at it but still doesn't get the case's math right. The main issue may be one of two things: Lack of preparation for consulting math, which is a very specific type of exercise, or nervousness under pressure. The lack of preparation may impact one or more areas of math exercises. The person doesn't know how to do mental math properly, how to structure a prompt in a logical way, how to calculate effectively or how to derive insights from the results. Nervousness under pressure, on the other hand, may be triggered by internal aspects related, for example, to the importance they give to that interview, among other more personal themes.
Let's take a deep dive into those potential problems one by one.
“I am just not a heavy math person…
When somebody is asking me to calculate something on the fly/spot I feel super overwhelmed and have felt a blockade.
My written math skills are ok but I have difficulties with mental math and basically feel not confident and secure in the quantitative field.” (taken from PrepLounge Q&A)
I believe anyone can become good at case math. When I was finishing high school, I was about to register for either Literature or English, as my interests were not related to math at all. I was actually a mediocre math student during high school, to be kind to myself, and only began to get close to math once I understood its value for my finances and for my career as a young adult. And I only began to like math because I got closer to it. As often happens, we tend to like that which we do understand, or that in which we are proficient. Nobody likes the feeling of losing a game over and over again, right?
Besides my personal example, I like the one set by Professor Barbara Oakley, the author of Learning How to Learn. She used to say she was “allergic to math,” as if numbers were some kind of deadly disease a person should run away from. She graduated in Literature and even joined the U.S. Army as a communications officer. But somewhere along the way, she realized she wanted something more. She set her sights on engineering, which meant she had to make peace with her old enemy, math. And not only did she make peace, she went from being someone who hated math to becoming a professor of engineering at the University of Oakland.
You may feel like you are out of your league and that you are a slow learner, two thoughts that may be confidence killers. Professor Oakley turns this idea completely around and shows how these can actually be strengths in your learning journey. If you are starting a new skill or a new job and suddenly feel that imposter syndrome creeping in, like you are the least qualified person in the room or that you somehow didn’t truly deserve this opportunity, embrace it. Oakley argues that having a beginner’s mind is exactly what helps you stay open to learning. On the other hand, being overconfident can make you ignore your mistakes, so humility becomes a strength, not a weakness. And when it comes to being a slow learner, she offers a beautiful analogy. She compares it to a race car driver and a hiker. The car may get to the finish line faster, but the hiker, moving slowly, gets to notice the details and absorb all that is seen more deeply.
My advice to those who label themselves as not suited for numbers is: First, believe you can do it, have trust in yourself and in the process. No pep talk here, you really have to quiet the negative inner critic to focus on improving this area.
Second, learn math and case math from the ground up to the more advanced aspects that may be required in a case interview. Below follows a synthesis of four steps recommended by Barbara Oakley in her book Learning how to Learn (2018) that helped me to learn and retain new concepts and may help you too.
When learning new ideas, it is important to shift between focus mode and diffuse mode. Focus mode is when you are fully concentrated, for example, while doing math drills. Diffuse mode happens when you turn away from the problem for a while, allowing your brain’s resting state to work in the background and make connections without you even noticing.
Then comes practice. Study consistently every day, even if it is just for 30 minutes. Using the Pomodoro Technique can help you stay focused and make sure you hit at least that daily mark.
After that, make sure you understand what you have learned by recalling it without any aid. Ask yourself: what formulas did I learn today? What are the concepts behind them? What are they useful for? This kind of active recall will strengthen your understanding much more than just rereading notes.
Finally, repeat. Do the same drills over and over again until you master them. You should be able to tackle them by heart, almost like that song that gets stuck in your head. Repetition makes the method second nature, and that is exactly what you want when you are solving math under pressure.
“(...) This was a partner interviewing me, and he gave me a case with a lot of numbers. My initial framework was good, he pushed back a bit, and I explained my reasoning. Then we get into the math. Not necessarily difficult math, just lots of multiplication. I said what I planned to multiply, then did the multiplication, and like 3 separate times came up with an extra 0 somewhere. This took awhile and he fast-tracked some future math (...). I can't shake the feeling spending the whole interview doing multiplication totally screwed up this whole thing. The funny part is, I'm a math major too.(...)” (taken from PrepLounge Q&A)
Lots of people with a quantitative background take case math for granted and discover that it is not that simple. Case math differs from academic math in different ways.
First, in academic settings, problems are often well-defined, allowing for deep, methodical analysis. In contrast, consulting case interviews demand rapid, approximate calculations under time pressure, often without calculators. This shift can be jarring for those accustomed to precise computations.
Second, quantitative experts might accidentally apply complex methodologies to straightforward problems, leading to inefficiencies. Case math is not supposed to be complicated, it is supposed to be difficult, yes, but solvable in an elegant and concise way.
Third, consulting problems often lack clear-cut solutions, requiring comfort with ambiguity and estimation, skills that might not be emphasized in quantitative academic training.
Finally, advanced quantitative work often relies on tools like calculators or software, which can lead to diminished mental arithmetic skills over time.
The path to solve this issue is simple: practice actual case math. Moreover, I suggest identifying where your main problem is so you can prioritize this issue. Consider that case usually has nine steps in the math portion. Check what is the step that is causing trouble:
After identifying the main issue, deep dive on it. Do drills from good casebooks and re-do old cases you've solved. In one hour you should be able to do at least three exercises from beginning to end, way more effective than spending one hour doing an entire case and only covering one exercise.
👉 Use our Mental Math Tool to practice and improve your calculation skills!
Now that we have talked about case math, let's talk about another aspect that may be preventing the quant type from showing their best self when it comes to the math portion of the interview. It may be the case that the person is fully prepared, has done the homework and is getting all math drills right. However, when it comes to mocks and interviews, nervousness stays in the way.
“I've noticed that I often get serious math nerves during case interview situations. The qualitative part comes easy for me, but I always mess up on the quantitative part. It's usually silly mistakes like 90% = .09, or 1*2 = 3... sigh…” (taken from PrepLounge Q&A)
That was my case (as I write this down I have to acknowledge that real life is not always MECE), in fact, this could have actually been written by an old me. As I said before, while at High School I was a mediocre quant student. However, at the University I turned out to be one of the best ones after understanding the value of it. Even having turned into a good math student, at case interviews I would get so nervous that even the simplest calculations appeared to be unsolvable. “100 divided by 25? Can you give me a minute please?”. That was frustrating.
What I did and recommend to people in the same position: first, master case math with proper drills, which we have already covered; second, practice with peers who can simulate the environment of a case interview; third, positive self-talk before the cases; and fourth, practice Emotional Freedom Technique (EFT), probably the most awkward item of this list – so let's take a closer look at it.
If you have never heard of it, EFT, also known as tapping, is a simple yet surprisingly effective method that combines gentle tapping on specific meridian points, similar to acupuncture, with verbal affirmations. It might look a bit odd when you first try it, believe me, I thought the same!, but it works.
A randomized controlled trial published in the Journal of Nervous and Mental Disease (Church et al., 2012) showed that just one EFT session reduced anxiety by 24%. That is a big deal, especially when you are preparing for something as stressful as a case interview. The logic behind EFT is simple. It helps you acknowledge your anxiety instead of suppressing it, while sending calming signals to your nervous system. This makes it easier to stay composed under pressure, even when the math gets tough or the stakes feel overwhelming.
For me, incorporating EFT before practice sessions helped shift my mindset from “I need to get this perfect” to “I’m calm, and I’m learning.” That change alone made a huge difference. So, if you find yourself spiraling into anxiety before or during a case interview, try a quick round of tapping. It may feel silly at first, but the results speak for themselves.
I talked about why confidence matters, why some people get their confidence shaken when it comes to math, the two most common types of people that have some issue in this matter and some tips on how to overcome the main math barriers.
So, to wrap this up, let me tell you this: math confidence is not about being born a genius or having some secret math gene. It is about knowing where you struggle, working on it step by step, and learning how to keep your cool when the stakes are high. Like that coach said, what really sets candidates apart is the confidence they project, even when things are not perfect. Whether you think of yourself as “allergic to math” or you have a fancy quant degree but still freeze when numbers show up, you are not broken, you are just human. And the good news is: you can change. With practice, consistency, and a bit of kindness to yourself, you will not just survive the case math, you will be able to face it with clarity and composure, and that is exactly what interviewers are looking for.
If this article resonated with you and you want help building your case math confidence, feel free to reach out. I’d be happy to work with you on PrepLounge, whether you need structured drills, feedback, or just someone to keep you accountable. Let’s make case math one less thing to stress about!'
Mariana is a case interview coach on PrepLounge and a former McKinsey consultant. She supports candidates throughout the consulting recruiting process – from crafting impactful CVs to mastering fit and case interviews – with a strong focus on structure, communication, and confidence.
