Free calculators, builders, and drills
Free Case Interview Tools
Calculators, builders, and one free AI-graded drill rep for the skills interviewers actually ask: math, structure, market sizing, charts, brainstorming, and synthesis.
Case Interview Structure Drill
MECE issue tree.
Start drillCase Interview Brainstorming Drill
Idea buckets.
Start drillCase Interview Math Drill
Formulas and mental math.
Start drillMarket Sizing Drill
Assumptions and sanity checks.
Start drillChart Interpretation Drill
Chart insight and so-what.
Start drillCase Synthesis Drill
Crisp recommendation.
Start drill
CAGR Calculator
Compute compound annual growth rate live. Used in growth diagnostics, market sizing reasonableness checks, and any case asking 'how fast does this grow?'
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Market Size Calculator
TAM, SAM, and SOM with editable assumptions, top-down/bottom-up toggle, and a built-in sanity check against GDP and per-capita spend.
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Breakeven Calculator
Units, revenue, contribution margin, and target profit - with the formula breakdown you narrate during the case.
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Profitability Tree Builder
Drag-and-drop Profit = Revenue − Cost tree with live AI feedback on MECE, depth, and cost-driver specificity.
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Case Structure Builder
5 MBB-canonical templates (profitability, growth, market entry, pricing, operations) plus AI feedback on your structure.
Open toolWant a full case?
Run a free AI-graded case interview
One full case, scored on structure, math, and synthesis. No card.
What free case interview tools should actually do
Most free case interview tools online are either too generic - a one-page math sheet that doesn't match the shapes a real interviewer asks - or too gated, where the "free" tool is really a 14-day trial that converts to a paywall once you start using it. The tools on this page are different: they are free or free to try, and modeled on the actual prompts that come up in MBB and Tier 2 first-round interviews.
The CAGR calculator, market size calculator, and breakeven calculator cover the three quantitative shapes that decide whether you clear the math phase of any case: growth, sizing, and unit economics. The profitability tree builder and case structure builder cover the two structuring shapes interviewers grade hardest - root-cause diagnostic and MECE framework. The AI drill tools add targeted reps for structure, brainstorming, math, market sizing, chart interpretation, and synthesis. Together, the set covers the core skills that get graded in a typical case interview, including McKinsey PSGs and BCG case rounds.
How to use these free tools in your prep
Run the math tools (CAGR, breakeven, market sizing) in short daily reps - five minutes a day under a clock beats one-hour weekend sessions. Run the structure tools (profitability tree, case structure builder) once a week, building a tree from scratch on a fresh prompt and getting AI feedback before you peek at any answer key. Pair the tools with the free templates on /free-resources to lock the operational layer of recruiting (resume, cover letter, tracker) so case prep isn't competing with application logistics.
Frequently asked questions
Are these case interview tools really free?
Yes. The calculators and builders open in your browser with no signup, no paywall, and no credit card. The AI drill tools include one anonymous AI-graded rep, then signup unlocks more drill practice and saved progress.
Which free tool should I start with?
If you have a case interview in the next two weeks, start with the case math practice tools (CAGR, breakeven) and the market size calculator. If you are early in prep, start with the case structure builder and profitability tree to internalize the shapes interviewers expect.
Do these tools work for MBB, Tier 2, and Big 4 firms?
Yes. The arithmetic and structure shapes are the same across McKinsey, BCG, Bain, Strategy&, Oliver Wyman, Kearney, LEK, and the Big 4 strategy practices. The tools are designed to MBB bar so they over-clear Tier 2 and Big 4 expectations.
What is the difference between these tools and Road to Offer Pro?
These tools are free forever. Pro adds unlimited live AI case interviews, behavioral interview simulation with feedback, full drill library access, and saved progress. Pro is the next step when you want adaptive, scored practice rather than self-led drilling.