Consulting Interview CheatSheet
This is my experience with consulting and creating interview cheatsheet.
I have had a varied career close to a decade. I wasn’t sure what career would be a right fit for me. And as they saying goes, when you don’t know what to do , DO consulting (just kidding , or maybe not :p) When I worked for a boutique consulting which focussed on tech and finance, that’s when I got to work on data engineering projects. This led me to work at a start-up as a solutions engineer with a start-up focussed on building data pipelines. Finally, working there gave me the perspective and direction to follow solutions engineering/architecting at PayPal. And all of this, wouldn’t have happened without consulting. Now, before you think that if you are an engineer, then consulting is not for you, then I would probably need to correct you. Because, from Big 4 (PWC, Deloitte, KPMG to Ernst & Young) to the Trinity (McKinsey , Bain and BCG), they all hire for tech consultants. And if there was ever a career to polish off and master soft skills, it was consulting. It teaches you diverse skills and more importantly, the ability to handle difficult use-cases in a short time and more importantly making a significant impact. Fun fact : Sundar Pichai , CEO of Google, worked as a consultant at McKinsey prior to joining Google.
Now, coming to interviewing , there are a lot of behavioral questions which will be asked. But the technical or strategy questions are the difficult ones. Unless you have studied for them.
There are two things I have learnt about consulting market sizing/casing questions over time :
They are meant to analyze your thinking. The interviewer is analyzing your thinking and strategy. As long as the answer is somewhere within a nearby ballpark, you are fine.
These questions in my opinion are to throw you off. Your ability to not be flustered and patiently work through the solution will determine your success
Market sizing (or Fermi estimation) questions test your ability to break down complex problems into logical, manageable steps. The most important things atleast for me in the beginning was to buy some time to think through. To do that , here’s what I would do. Explaining with the help of an example :
“How many tennis balls can fit in a plane ?”
Buying Time Strategy :
The best way to buy time is to :
Clarify the question :
This could be by clearing up the questions :
Are we talking about a commercial plane or a private jet ?
Making Assumptions :
Then the next section is to make and confirm assumptions :
Is the a tennis ball is ~7 cm in diameter ?
What would be the dimensions of the plan ? (e.g., 747’s length ≈ 70m, width ≈ 6m, height ≈ 4m).
Is it okay to use approximations for calculations ? For example after calculating area of plane and area of ball, round up to whole numbers for simpler calculations.
Apply constraints :
Consider unusable spaces (seats, cockpit, storage).
Assume that only 70% of the plane is usable.
By applying the above three principles which I remembered as CAC (Clarify , Assume , Constraints) , I would buy time but more importantly show strategic thinking. This helped me think through the problem, present structured approach to all of the questions asked.
Having clarified assumptions , then it was time to deep dive and solve.
If your calculations are fine , then at the end of the day, all you need to do is :
Result = Area of plane / Area of 1 ball.
Sharing result below :
• Tennis ball: Diameter ≈ 7 cm → Volume = \frac{4}{3} \pi r^3 ≈ 150 cm³
• Boeing 747 Interior Volume: Approx. 800 m³ (~800,000,000 cm³)
• Packing Efficiency: ~70% (stacking inefficiencies)
• Final Estimate: \frac{800,000,000 \times 0.7}{150} ≈ 3.7 million balls
⸻
2. Market Sizing Questions Cheat Sheet (Common Formulas & Assumptions)
A. Volume-Based Estimation (e.g., “How many tennis balls fit in a plane?”)
Formula:
Number of objects = Total size of another object / size of 1 object.
Common Assumptions:
• Tennis ball: Diameter ≈ 7 cm → Volume = \frac{4}{3} \pi r^3 ≈ 150 cm³
• Boeing 747 Interior Volume: Approx. 800 m³ (~800,000,000 cm³)
• Packing Efficiency: ~70% (stacking inefficiencies)
• Final Estimate: \frac{800,000,000 \times 0.7}{150} ≈ 3.7 million balls
⸻
B. Population-Based Estimation (e.g., “How many barbers are in New York City?”)
Formula:
\text{Total Demand} = \text{Population} \times \text{Service Frequency per Capita}
Common Assumptions:
• NYC Population: ~8M
• Haircuts per person per month: ~1 (Men), ~0.5 (Women) → Avg: ~0.75
• Total haircuts/month: 8M \times 0.75 = 6M haircuts/month
• Haircuts per barber per day: ~10 (200/month)
• Barbers Needed: \frac{6M}{200} ≈ 30,000 barbers
⸻
C. Consumption-Based Estimation (e.g., “How many pizzas are sold in the U.S. per year?”)
Formula:
\text{Annual Demand} = \text{Population} \times \text{Avg Consumption Per Capita}
Common Assumptions:
• U.S. Population: ~330M
• Avg pizzas/person/year: ~25
• Total pizzas/year: 330M \times 25 = 8.25 billion pizzas/year
⸻
D. Area-Based Estimation (e.g., “How many golf courses are in California?”)
Formula:
\text{Total Land Area} \div \text{Avg Land per Unit}
Common Assumptions:
• California land area: ~400,000 km²
• Avg land per golf course: ~1 km²
• Estimated golf courses: \frac{400,000}{1} ≈ 4,000 golf courses
⸻
Casing Questions :
Currently taking into 4 types :
Profits & Loss: Revenues:
Entering a new market
Pricing
Growth and Increasing Sales
Profits and Loss Revenue :
Scenario: A mid-sized online clothing retailer wants to analyze their profit and loss for the last two quarters.
Clarifying Questions:
Start off with clarifying questions : You need analyze profits and loss. This means, can you think about revenues and costs. So, accordingly the clarifying questions follow :
What are the primary revenue streams (e.g., men's wear, women's wear, accessories)?
What are the fixed vs. variable costs?
Has there been any marketing push or product launch recently?
Are we comparing quarters, or year-over-year?
Assumptions Made:
Revenue comes from 3 streams: Men’s (40%), Women’s (50%), Accessories (10%).
Costs include manufacturing, marketing, logistics, and platform fees.
Industry-standard gross margin is 60%.
Applying Constraints:
Limit analysis to Q3 and Q4 only.
Benchmark only against top 3 competitors in the U.S. online retail market.
Example Walkthrough:
Revenue in Q3 was $10M, and in Q4 it increased to $12M. But profit dropped from $2.5M to $1.5M.
On inspection, marketing costs rose from $1M to $3M in Q4. A deep dive shows an aggressive ad campaign underperformed.
Accessory revenue dropped by 50%, indicating potential inventory or pricing issues.
Benchmarking shows the client’s shipping cost per order is $2 higher than competitors due to inefficient last-mile delivery.
Insights: Unusual increase in marketing spend and high shipping costs are squeezing profit. Accessory line underperforming may suggest poor product-market fit.
Entering a New Market Example
Scenario: A U.S.-based edtech company wants to expand into Latin America via acquisition.
Clarifying Questions:
Think about the overarching goal here.
What is the goal: user growth, revenue, or diversification?
What companies are being considered for acquisition?
What’s the regulatory landscape?
Assumptions Made:
The company wants to acquire a mid-sized local edtech firm in Mexico.
Cultural fit is critical as the client values collaborative work culture.
Applying Constraints:
Must enter the market within 6 months.
Budget capped at $10M.
Example Walkthrough:
The client shortlists two Mexican firms: Firm A (good growth, weak brand) and Firm B (moderate growth, strong brand, but hierarchical culture).
Due diligence reveals Firm A uses similar technology and agile processes, ensuring faster integration.
Firm B would require a major cultural shift.
Financial modeling shows both firms will break even in 2 years, but Firm A will yield better long-term synergies.
Insights: Although Firm B has stronger brand recognition, Firm A is a better cultural fit and aligns with the company’s long-term agility goals.
Pricing Example
Scenario: A SaaS startup is launching a project management tool and needs to decide pricing.
Clarifying Questions:
What is the customer segment (e.g., freelancers, SMEs, enterprises)?
What are competitors charging?
What are our development and support costs?
Assumptions Made:
Targeting SMEs.
Direct competitors charge $10-$15/user/month.
Our cost per user is $5/month.
Applying Constraints:
Need to reach break-even in 12 months.
Cannot exceed $15/user/month due to market cap.
Example Walkthrough:
Competitive analysis shows our tool has superior features but lacks brand presence.
Cost-based pricing would suggest $7/user/month to maintain 40% margin.
Price-based costing shows SMEs are willing to pay $12 if onboarding is easy.
Final pricing decision: Offer $10/user/month, with a 3-month free trial to lower adoption barrier.
Insights: The pricing strategy balances cost recovery and market competitiveness while encouraging trial and word-of-mouth marketing.
4. Growing and Increasing Sales Example
Scenario: A boutique coffee brand wants to grow its online sales by 30% over the next year.
Clarifying Questions:
What are current sales channels and performance?
What’s the size of the target market?
How do our prices compare to competitors?
Assumptions Made:
Current annual revenue is $2M, mostly from online DTC (Direct to Consumer).
Industry CAGR is 5–7%.
Applying Constraints:
Marketing budget increase limited to 10%.
Maintain premium pricing; no discounting strategy.
Example Walkthrough:
Company invests in SEO and influencer partnerships instead of discounts.
Expands SKUs with a limited-edition single-origin series to create buzz.
Conducts a competitor analysis: client’s pricing is 20% above average, justified by quality and sustainable sourcing.
Uses email campaigns to target repeat customers and improve retention.
Insights: Focused growth via product line extension and customer engagement (rather than price cuts) allows premium branding and sales uplift.
Some more excellent use-cases to master this and use :
The article is a continued piece and I aim to add more updates as I get a chance to refine it. Hope this is helpful.