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Solving the problems by calculating the area of the triangle
Profit / breakeven formula
Correlations, outliers (being able to spot on the graphs, tables)
2) Fast math skills
Rounding up and down
Learn how to multiply double digit numbers (https://www.youtube.com/watch?v=6ndkkPZYJHo)
Learn the division table up to 1/11 (i.e. 5/6 = 83.3)
Learn how to work with zeros using powers (e.g.: 4000000 = 4*10ˆ6)
Use math tools (Mimir math for iOS), Math tool on Viktor Cheng website to practice
3) Working with tables and graphs and deriving conclusions
Study "Say it with Charts" book
Check all available MBB presentations and publications. Practice to derive conclusions and check yourself with the actual ones from the article / presentation
GMAT IR part (Official guide and Manhattan prep)
Learn basic statistics (Any GMAT or MBA prep guides)
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Hi Anonymous,
these are the most common formulas I encountered/have been useful through my interview process at BCG:
Breakeven point
Rule of 72 (for quickly computation of compound rates)
Perpetuity formula (for quick valuation estimates) and general NPV formula
I would not expect any interviewer to provide any of them in case you don’t know (or if they provide I don’t think they would move you to the next round).
Besides that, you should also be familiar with simple and compound interest, and could be useful to be updated on the main currency exchanges, oil and gold prices.
Finally would recommend reviewing the formulas for volume/surface of main solid figures (pyramid, cone, cylinder, sphere), which could be useful in market sizing cases.
• Debt-to-Equity Ratio = Total Debt / Total Equity
• Four Cs (marketing from a customer’s point of view): Convenience, Cost to the user, Communication, Customer needs and wants
• Four Ps (starting or expanding a business): Product, Price, Place, PromotionGross Profit = Sales – Cost of Goods Sold
Gross Profit Margin = Gross Profit / Total Revenue
• Profit = Total Revenue – Total Costs
• Return on Assets = Net Income / Total Assets
• Return on Equity = Net Income / Shareholder’s Equity
• Return on Investment = Net Income / Initial Investment
• SWOT Analysis: Strengths, Weaknesses, Opportunities, ThreatsTotals Costs = Fixed Costs + Variable Costs
• Total Revenue = Price x Volume
Very interesting, for North America perspective I find requirements for financial knowledge to be wildly different from the ones outlined in other answers.
Unless you are an MBA, a finance major or worked in finance I do not expect any knowledge of the formulas - with the exception of NPV - and I will indeed explain the relevant formulas to you if needed. Also would never expect you to calculate the NPV of a series of cash-flows during an interview due to the computational heaviness of that.
Finally, the rule of 72 is a nice tool but if candidate uses it during the interview then I would ask the mathematical explanation behind it. If you don’t that would be detrimental. This because To be an excellent consultant is very important that you know and understand the tools that you use intimately and understand how they work, their limitations, etc.
What I do expect is that you ace the basics like multiplications and divisions. I know, it sounds, well, basic, but if you have an hesitation on telling me what is 2% of 5M or calculate 0.6/9 that would be almost a non starter.
Finally when we do math I would like to see if you can get to the results in the simplest and fastest way possible. This will show me whether in a case you are trying to complicate things uneccessarely.
After +5 years of candidate coaching and university teaching, and after having seen hundreds of cases, I realized that the economic-related knowledge needed to master case interviews is not much, and not complex. However, you need to know where to focus! Hence, I created the guide that I wish I could have had, summarizing the most important economic and financial concepts needed to solve consulting cases, combining key concepts theorical reviews and a hands-on methodology with examples and ad-hoc practice cases.
It focuses on 4 core topics, divided in chapters (each of them ranked in scale of importance, to help you maximize your time in short preparations):
Economic concepts: Profitability equation, Break even, Valuation methods (economic, market and asset), Payback period, NPV and IRR, + 3 practice cases to put it all together in a practical way.
Financial concepts: Balance sheet, Income statement/P&L and Performance ratios (based on sales and based on investment), +1 practice case
Market structure & pricing: Market types, Perfect competition markets (demand and supply), Willingness to pay, Pricing approaches, Market segmentation and Price elasticity of demand, +1 practice case
Marketing and Customer Acquisition: Sales funnel, Key marketing metrics (CAC and CLV) and Churn, +1 practice case
Feel free to PM me for disccount codes for the guide, and I hope it helps you rock your interviews!
You may use math structures while problem-solving during the case. For example, if you have to understand why our factory has 4 FTEs doing the cleaning while Competitors use just 2 FTEs, you can structure it like:
Frequency of cleaning per day * working days * FTEs per 1 cleaning
After deriving the numbers you may find that a single cleaning procedure is longer and you may want to check if the problem is in: People / process / technology
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Fast Math
Math plays a big role in case interviews because it helps you solve business problems logically and in a structured way. It’s not about applying complex formulas; it’s about working quickly with numbers and finding practical solutions. Since you won’t have a calculator and can only use pen and paper, knowing effective calculation methods is key. These skills show off your analytical mindset and can make you stand out from other candidates. Why Mental Math is a Big PlusIn case interviews, being able to handle basic calculations in your head is a huge advantage. It saves time and makes you appear more flexible and confident. It’s not about avoiding writing things down entirely, it’s rather about quickly grasping the results. The goal is to get a fast overview and deliver precise answers. Imagine calculating revenue and profit for multiple products – if you can confidently do these calculations in your head, you’re already a step ahead. Working with Rounded NumbersIn case interviews, you’ll often see “rounded” numbers like 300,000 or 4,000,000. Working with large numbers can feel intimidating, but a few simple tricks can make it much easier.💡 Quick Trick: Cutting ZerosLet’s say you’re calculating the revenue for a product that a company sells at $32 per unit, with 25,000 units sold annually. The calculation is 32 × 25,000. Instead of writing all those zeros, break it into simpler steps:Calculate 32 × 25 first, which is easier than 32 × 25,000.Then, just add the three zeros from “25,000” to the result.To quickly solve 32 × 25, you can think of 25 as ¼ × 100:32 × ¼ = 88 × 100 = 800So, 32 × 25 is 800, making 32 × 25,000 equal to 800,000. This method saves time and reduces the chance of misplacing zeros. Adding and Subtracting with UnitsLarge numbers, like 250 million or 300 million, might seem challenging at first glance. A useful technique is to work with units like thousands (K), millions (M), billions (B), and trillions (T). This simplifies addition or subtraction because you don’t have to write out or imagine all the zeros.💡 Quick Trick: Adding Large NumbersSuppose you need to add 250 million, 300 million, and 150 million. Instead of writing each number fully, just add the leading numbers and keep the unit:250 + 300 + 150 = 700, then add the “million” unit."The result is 700 million. This approach is quicker and reduces errors since you’re focusing only on the main numbers, not all the extra zeros. Multiplication and “Clean Numbers”Multiplication is common in case interviews, and many numbers used are “clean numbers”, meaning they have helpful properties that make calculations easier. For example, 25 is a “clean” number because it’s ¼ × 100, which simplifies large multiplications.💡 Quick Trick #1: Fast-Math Multiplication:The Fast-Math Method is a technique for simplifying complex multiplications by breaking them into easier steps. It’s based on the idea that you can halve one number and double the other without changing the result, thanks to the commutative property of multiplication. This keeps the final product the same but often makes the math easier. Here’s an example:Original calculation: 160 × 350Halve 160: 160 ÷ 2 = 80Double 350: 350 × 2 = 700Multiply the results: 80 × 700 = 56,000The result is the same as 160 × 350 but without lengthy calculations. This method is especially handy in case interviews, allowing for quick, error-free calculations.💡 Quick Trick #2: Reordering Multiplication Factors:Another helpful technique is rearranging terms to make the multiplication easier. Imagine you need to calculate 125 × 2.5 × 4. You can rearrange like this:Start with 125 × 4 = 500.Then, 500 × 2.5 = 1,250.The answer is 1,250. Reordering simplifies the calculation. You could also do 2.5 × 4 = 10, then 125 × 10 = 1,250. This flexibility lets you choose the easiest order for each case. Quick Calculations for Percentage GrowthLet’s say a company grows 4% per year. Calculating this over multiple years can often be simplified by ignoring compound interest and estimating growth. This is especially helpful for shorter time periods and moderate growth rates.Example: Estimating Percentage GrowthIf a company’s revenue is $400 million and it grows at 4% annually for six years, you can estimate the growth like this: 4% × 6 = 24%, which is roughly one-quarter. So the revenue grows by about 25%, or around $100 million, bringing it to about $500 million after six years. This method gives a quick estimate for growth impact over several years. The Net Present Value (NPV) MethodThe Net Present Value (NPV) method is a common approach to calculate the current value of a future investment. It helps determine today’s value of expected cash flows by discounting future payments. A positive NPV indicates a worthwhile investment, as future returns exceed the initial cost.💡 Quick Trick: Rule of 72The “Rule of 72” is a tool for estimating the doubling time of an investment—how long it’ll take to double in value. The Rule of 72 uses the exponential growth formula and can be applied when a rate of return (or growth rate) is known.Simply divide 72 by the annual interest rate (in percent) to estimate the doubling time. For example, if the growth rate is 6% annually, the investment doubles in about 12 years (72 ÷ 6 = 12).This quick estimation helps estimate the future value of an investment without needing to apply the exact NPV formula. Since it’s an approximation, it’s great for quick decisions or rough estimates but less suited for precise calculations.Example: NPV of a Real Estate ProjectA real estate company is considering a project that will sell apartments for $250 million in six years. What’s the current value of this investment if they expect a 12% return annually? Using the Rule of 72, an investment with a 12% growth rate doubles in about six years (72 ÷ 12 = 6). So, today’s value is roughly half the future value, or $125 million. This means the company should invest no more than $125 million to achieve a 12% return. ConclusionMath and quick calculations are essential in case interviews to help you stand out from other candidates. The methods and examples here allow you to tackle common calculations efficiently and accurately. From working with rounded numbers to using the Fast-Math Method, these techniques make you faster and more confident with numbers. Practice these methods before your interview to be flexible and confident, showcasing your math skills effectively.👉 Elevate your math skills to the next level by practicing with our Mental Math Tool!
The BCG Online Case has now been rolled out globally and has replaced the BCG Potential Test in all but a few offices. So if you're applying to BCG, you'll probably have to take the new BCG Online Case. In the BCG Online Case (also called the Chatbot Interview), a chatbot named Casey presents you with a real case, similar to the one you might receive from human interviewers.However, because it's a chatbot interview, the case is not guided by an interviewer, which means you have little to no control over the process.The case contains 8 to 10 questions that are asked through an instant messenger-like interface and must be solved in 25 to 30 minutes. These questions take 2 forms:Multiple-choice questions where candidates must select what data they need to move forward, what analysis they want to do next, or what their findings/conclusions areOpen-ended questions where candidates must explain their answers to the previous multiple-choice questions or answer a math or creative questionAfter this procedure, there is a one-page video interview question at the end where you are asked to make a recommendation. You have 1 minute to prepare and another minute to present your conclusion to the client. Because there are open-ended explainer questions, your score is not as easy as other, more traditional screening tests like the McKinsey Imbellus and the BCG Potential Test. Instead of a standardized score (i.e., how many questions a candidate answered correctly), you will likely be evaluated holistically on the key consulting competencies mentioned earlier, and your performance will be compared to that of other candidates.You will receive your results within 2 weeks. In some cases, the test is given as part of the first round interviews. Your performance in the test will be evaluated together with your performance in the case interview. You will then be notified of the results accordingly.You only have one chance to pass the new test - if you don't pass, you can't try again for another 1 to 2 years. Therefore, it is important that you prepare yourself very well to master the case.The differences from the BCG Potential Test are as follows:Calculators are allowedOnly 25-30 minutes to solve the case instead of 45 minutes8-10 questions instead of 23Open-ended questions instead of multiple-choice questionsIt ends with a video summary*box-open* In our shop you will find everything you need to prepare for your case interview at BCG! Among other things, you can get the helpful BCG Online Case Combo and the BCG Online Case Secrets. *box-close*The skills that will be assessed are math skills, structuring, interpreting graphs, business acumen, and synthesisBCG's basic hypothesis in introducing this test is that if you do well in these areas, you should also do well in a real case interview and in live situations with the client.You should master the following key skills:Structured Thinking: You must be able to break down complex problems into smaller, manageable pieces and develop a clear structure for solving the problem.Analytical Skills: You must be able to quickly analyze and interpret data to gain insight and make informed decisions.Creativity: you must be able to develop creative solutions and find alternative approaches to solve complex problems.Communication: You must be able to communicate your thoughts clearly and concisely, and explain complex concepts in an understandable way.Time Management: You must be able to plan and prioritize effectively to make efficient use of the time available.Collaboration: you must be able to work with others and foster effective teamwork to develop collaborative solutions.If you master these key skills and prepare specifically for the BCG Online Case interview, your chances of a successful interview are good.
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