Most candidates build a bookmark folder of "free tools" and never open the practice cases the firms publish for free. That is backwards. The interviewer's scoring sheet rewards the format those cases already encode: structure, math under mild pressure, exhibit reads, and a clean recommendation. Calculators and drill rooms come after.
This guide is the wider free-tools map. Sister piece CoachNed Free Tools covers the equation side — free calculators teach the equation; the room grades the spoken so-what. Here you get the order of operations: firm-owned practice and assessment demos first, public statistical offices for market-sizing anchors second, then CoachNed's free surfaces described plainly. No competitor prep directories.
After reading, you should be able to pick one firm case, one census table, and one timed CoachNed surface for the next seven days without expanding your bookmark bar.
Why firm-owned free practice beats a tool pile
When I score a first round of eight, three candidates usually look polished on frameworks and still fail the format. They pause too long for a memorized tree. They treat exhibits as reading comprehension. They give a recommendation that never names the decision metric.
Firm practice cases fix that faster than another generic drill pack because they are written in the firm's dialect. McKinsey's sample cases walk a structured problem-solving conversation with suggested answers. Bain's interactive Coffee Shop Co. and FashionCo cases force a go/no-go or revenue-recovery recommendation with explicit arithmetic. Deloitte's practice tool states it is not tracked — you can grind it — and still mirrors how they want you to move through a client situation.
I am not claiming these pages reveal confidential scoring keys. They do not. They do reveal what each firm is willing to put on a public careers URL, which is more useful than folklore from anonymous boards.
Layer one: the firms' free practice cases and demos
Start here if you have an invitation, or if you are targeting that firm this cycle. Use the official careers pages, not mirrors.
| Firm | What is free on their site | Best use this week |
|---|---|---|
| McKinsey | Sample problem-solving cases (for example Diconsa) plus Solve assessment overview | One full sample case out loud, then read the suggested logic |
| BCG | Case interview prep guidance; OneDay@BCG free job simulations; CCA / online case described on recruiting FAQs | OneDay module for process feel; live case practice for the room |
| Bain | Coffee Shop Co. and FashionCo interactive cases; digital assessment hub (Sova / TestGorilla by office) | CoffeeCo for break-even math; FashionCo for option comparison |
| Deloitte | Interactive case practice tool (~15–20 min); separate scenario tool for some tracks | One consulting case end-to-end; say answers aloud, not only click |
| Oliver Wyman | Interview prep page with practice case samples (oil and gas, supermarket pharmacy, and others) | One OW case with their six-step method written on paper |
| L.E.K. | Interview prep page with brewery, pharma sizing, and brainteaser prompts | Large Pharma Co. sizing spoken in under eight minutes |
McKinsey's interviewing hub explains the problem-solving interview and points you to sample cases with logic and suggested answers (Interviewing at McKinsey). Solve, the gamified assessment, has its own page; McKinsey's public line is to approach it with curiosity rather than grind prep (Solve overview). Treat sample cases as the free practice; treat Solve folklore as folklore.
BCG's case prep page frames the case as a realistic client challenge and links OneDay@BCG, a free virtual experience with multiple job-simulation modules (BCG case interview preparation; OneDay@BCG). Office-level FAQs describe the Consulting Career Assessment (CCA) and online case (often ~30–35 minutes) when those gates apply. Follow your invitation for the exact product; public pages do not freeze one global format.
Bain publishes Coffee Shop Co. and FashionCo on its case interview prep page (Bain case interview preparation; Coffee Shop Co.; FashionCo). CoffeeCo walks break-even against market cups; FashionCo compares a rewards program versus intermittent sales with explicit revenue math. For the digital assessment, Bain's hub states you may see Sova or TestGorilla depending on office, and points Sova candidates to the provider's preparation area (Bain digital assessment).
Deloitte US links an interactive practice case tool and a scenario tool for some entry-level tracks (Deloitte case and scenario tips; Deloitte case interview prep tool). Oliver Wyman's entry-level interview prep page lays out a six-step case method and links practice samples such as the oil and gas price strategy case (Oliver Wyman interview preparation). L.E.K. publishes brainstorming-style prompts and classical cases — brewery profits, large pharma market size and pricing — on its interview preparation page (L.E.K. interview preparation).
Ned's rule. Before you open any third-party drill, finish one firm-authored practice case for every firm on your shortlist this month. If you cannot name which firm case you did last, you are collecting tools, not preparing.
Layer two: free public data for market sizing
Interviewers do not expect you to memorize every census table. They do notice when your population base is invented from thin air. Public statistical offices give you free, citable anchors.
| Source | What to pull | Typical case use |
|---|---|---|
| U.S. Census Bureau / data.census.gov | Population, households, age, income for metros and counties | U.S. consumer and B2B addressable bases |
| Eurostat database | Population by age and country; household and retail series | EU market sizes without inventing 450 million Europeans |
| ONS population estimates | UK mid-year population (provisional mid-2025 UK total about 69.5 million) | UK consumer, NHS-adjacent, and local retail cases |
Use the table for the base, then apply transparent filters: age band, income, category penetration, purchase frequency, average spend. Say the filter rates out loud. That is the skill the room grades — not whether you downloaded a CSV.
Worked sizing: dog daycare seats in Austin
Invented client: PawLane Daycare wants a rough annual revenue for a single location in Austin, Texas, before lease negotiations. Reproduce the arithmetic; your penetration rates can differ if you defend them.
Start with a metropolitan population you would look up on data.census.gov before interview day. For this exercise, use a round figure a candidate might reasonably state after a quick look: about 2.4 million people in the Austin–Round Rock CSA (state the source if you used a real pull). Households at roughly 2.5 people each: 2.4M / 2.5 ≈ 960,000 households.
Assume 35% of households own at least one dog (state it as an assumption, not a fact): 960,000 × 0.35 ≈ 336,000 dog households. Assume 12% of those would consider paid daycare in a given year: 336,000 × 0.12 ≈ 40,300 interested households. Assume your catchment covers 8% of the metro (drive-time): 40,300 × 0.08 ≈ 3,220 households in reach. Assume 25% convert to regular users: ≈ 805 households. Average 1.2 dogs per enrolled household: ≈ 966 dogs. Two days per week, 48 weeks, $45 per dog-day: 966 × 2 × 48 × 45.
Math: 966 × 2 = 1,932 dog-days per week. × 48 ≈ 92,700 dog-days per year. × $45 ≈ $4.2 million of theoretical catchment revenue. Capacity at 80 dogs per day × 2 shifts is far smaller — say 160 dog-slots × 250 operating days ≈ 40,000 dog-days, so facility-constrained revenue ≈ 40,000 × $45 = $1.8 million. The interesting answer is not $4.2 million. It is "demand looks larger than one site; the decision metric is fill rate and lease cost against $1.8 million capacity."
That is what free census data buys you: a defensible base so the interviewer can argue about filters and capacity instead of your population fantasy.
Layer three: CoachNed's free surfaces, described plainly
Once the firm case and one sizing anchor are done, use CoachNed where a timed, scored rep actually helps. Sibling hub: CoachNed free tools. Paths that stay useful without turning this into a product tour:
| Surface | What it is | When to open it |
|---|---|---|
| /start | Five-minute first rep: three typed turns of a case, instant scores, no account | Diagnostic before you invent a week-long plan |
| /drills/quick-math | Quick math drills; free forever after the open week | Daily ten-minute arithmetic rust removal |
| /tools and /tools/* | Calculators (market size, breakeven, CAGR), structure builder, issue trees, market-sizing questions, CCA-style numericals | After a mock flags a specific leak |
| /resources and /resources/* | Resume and cover templates, PEI workbook, casebook vault, application tracker | When the bottleneck is the packet, not the case |
Access, stated honestly: everything is open for seven days, no card; then $120 for a recruiting season or $49 a month. Quick math stays free forever. CoachNed is independent of McKinsey, BCG, Bain, Deloitte, Oliver Wyman, and L.E.K.
Which layer to open after a weak mock
Write the failure as a behavior, then pick one free action.
| What broke | Free next step | Skip for now |
|---|---|---|
| Format felt foreign (pacing, question types) | One firm practice case for that firm | Calculators |
| Population base was invented | Census / Eurostat / ONS pull, then re-size | Another full case |
| Arithmetic slow or wrong units | /drills/quick-math for ten minutes | New templates |
| Opening structure was generic | Firm case structure notes, then /tools/case-structure-builder | Bookmarking more case PDFs |
| Recommendation never named the metric | Re-do Bain CoffeeCo or FashionCo recommendation aloud | Reading tips articles |
Practice this week
Ninety minutes, three artifacts:
- Open the firm practice page for your top target. Complete one sample case out loud with a timer. Write the recommendation in four lines: decision, why, risk, next step.
- Pull one population or household figure from Census, Eurostat, or ONS for a market you might size. Save the URL and the as-of date.
- Run /start once. If math or sizing scored soft, spend ten minutes on /drills/quick-math or the market-sizing drill above. If structure scored soft, rebuild the opening on paper before the next full case.
Do not add a fourth tool until those three artifacts exist.
Frequently asked questions
Are free firm practice cases enough to get an offer?
No. They calibrate format and expectations. Offers still require live cases under pressure, behavioral stories, and enough volume that your structure does not freeze. Use firm cases as the free format tutor, then timed reps.
Should I prepare for McKinsey Solve with third-party games?
McKinsey's public Solve page emphasizes curiosity and integrity rules over grind prep. Treat unofficial "Solve trainers" as optional entertainment. Prioritize sample problem-solving cases and ordinary case math.
Where do free public data sources stop helping?
Interviewers do not expect you to memorize every census table. They do notice when your population base is invented from thin air. Public statistical offices give you free, citable anchors.
When you spend more time hunting tables than stating filters. One solid population or household base plus three transparent rates beats a fifteen-tab spreadsheet you cannot narrate.?
Start here if you have an invitation, or if you are targeting that firm this cycle. Use the official careers pages, not mirrors.
Do I need CoachNed if the firms already give free cases?
Only if you want timed, scored practice and calculators that force the spoken so-what. Firm cases do not grade you. /start and the drill rooms do. Many candidates combine both.
How many free tools should I keep on my bookmark bar?
Three maximum for any given week: one firm practice URL, one statistical office, one CoachNed surface. Everything else waits until those three change a behavior.
Sources
- Interviewing at McKinsey — sample problem-solving cases and interview overview. Checked 2026-09-24.
- Solve, McKinsey's assessment game — official Solve description and integrity rules. Checked 2026-09-24.
- McKinsey Diconsa practice case — example sample case with questions. Checked 2026-09-24.
- BCG case interview preparation — BCG case framing and OneDay link. Checked 2026-09-24.
- OneDay@BCG — free BCG job simulations. Checked 2026-09-24.
- Bain case interview preparation — Bain sample cases hub. Checked 2026-09-24.
- Bain Coffee Shop Co. — interactive break-even practice case. Checked 2026-09-24.
- Bain FashionCo — interactive revenue-recovery practice case. Checked 2026-09-24.
- Bain digital assessment — Sova / TestGorilla by office. Checked 2026-09-24.
- Deloitte case and scenario interview tips — links to practice tools. Checked 2026-09-24.
- Deloitte case interview prep tool — interactive consulting case practice. Checked 2026-09-24.
- Oliver Wyman interview preparation — case method and practice samples. Checked 2026-09-24.
- L.E.K. interview preparation — brewery, pharma, and brainteaser prompts. Checked 2026-09-24.
- U.S. Census data.census.gov — free population and household tables. Checked 2026-09-24.
- Eurostat database — EU statistical datasets. Checked 2026-09-24.
- ONS population estimates — UK mid-year population series. Checked 2026-09-24.