Short answer
A solid written case practice plan takes four weeks at about five hours per week: week 1 builds business reading, week 2 calculator-free math, week 3 exhibit interpretation, and week 4 full timed sets with error review. The McKinsey PST is retired, but these skills prepare you for McKinsey Solve, other firms' tests and case interviews.
Key takeaways
- Written case performance rests on three skills: business reading, mental math and analytical reasoning.
- Train each skill in isolation for one week, then combine them in timed sets in week 4.
- Review every error by type (reading, math or objective) and fix the most frequent type first.
- The McKinsey PST is retired; the same plan prepares you for Solve and for written cases at other firms.
The plan in one paragraph
Give yourself four weeks and about five hours per week. Spend one week each on business reading, calculator-free math and exhibit interpretation, then use the fourth week for full timed sets and error review. This plan grew out of how I prepared for the McKinsey PST and how I later coached candidates for it.
The PST is retired. McKinsey now screens with Solve, a gamified assessment, and other firms use written cases, numerical tests or chatbot cases. All of them reward the same three skills, so the plan applies to all of them.
The three skills you are training
Every written case test I have seen, and every Solve game candidates describe, draws on three abilities.
- Business reading: extracting the relevant fact from a dense paragraph or a long data set, quickly and without misreading.
- Mental math: percentages, growth, ratios and break-even, done accurately without a calculator.
- Analytical reasoning: deciding which conclusion the data supports and which answer serves the client's objective.
Most candidates are strong in one and weak in another. The plan trains each in isolation first, because combining them before the basics are solid only multiplies errors.
The 4-week training plan
| Week | Focus | Daily drill (about 45 minutes, 5-6 days) | End-of-week check |
|---|---|---|---|
| 1 | Business reading | Read one long business article; write the main claim and the three supporting facts in two minutes | Summarize a new article in under 90 seconds with no factual errors |
| 2 | Mental math | 15 minutes of arithmetic drills plus 30 minutes of business calculations (margins, growth, payback) | 20 business calculations in 15 minutes, at least 90% correct |
| 3 | Exhibits and charts | Interpret 8-10 charts and tables: state the key insight in one sentence, then answer one calculation question per exhibit | One sentence and one correct number per exhibit in under 2 minutes |
| 4 | Timed sets | Two full timed practice tests, plus shorter 20-minute sets on other days; review every error | A full 26-question set at 80% or better with time to spare |
Week 4 matters most. Many candidates practice for weeks but never simulate the clock, and then lose a full case to pacing on test day.
Week 1: business reading
Use quality business journalism and company annual reports. Read a piece, close it, and write down the central claim and the three facts that support it. Then reopen it and check.
Two traps to train out: confusing a percentage with a percentage point, and mixing up revenue and profit. Both appear in nearly every written case test.
Week 2: mental math
Daily drills beat long weekend sessions. Practice the operations that recur in business problems: percentage change, compound growth over two or three years, margin calculations, unit conversions and simple break-even.
Use rounding consciously. Round when the answer options are far apart; calculate exactly when they are close. My case interview math guide lists shortcuts for each operation.
Week 3: exhibits and charts
Collect charts from business reports and practice materials. For each one, follow the same routine:
- Read the title, axes and units before looking at any data.
- Note whether values are absolute or relative, and the time period.
- State the single most important insight in one sentence.
- Answer one calculation question that requires combining two data points.
That routine takes about 90 seconds once it is automatic, and it prevents the most expensive error in written cases: reading the wrong unit.
Week 4: timed sets and error review
Take two full timed tests on different days, in a quiet room, with only paper and pen. After each test, sort your mistakes:
- Reading errors: you answered a different question than the one asked.
- Math errors: the method was right, the arithmetic wrong.
- Objective errors: you picked an answer that was true but did not serve the client's goal.
- Time errors: you guessed or skipped because the clock ran out.
Fix the largest category first. On the days between full tests, run 20-minute mini-sets focused on that category. My original sample set is a good warm-up for a mini-set.
Stephan's note: The candidates I coached improved most in week 4, and almost all of that came from the error review. A test you never review mostly trains your nerves.
Adapting the plan for Solve
If your next test is McKinsey Solve, keep weeks 1-3 as they are. In week 4, add two sessions on the official Solve information: read McKinsey's page and review the rules (no apps, websites, AI tools or pre-prepared notes; work alone). Practice data-filtering under time pressure, because candidate reports describe Redrock Study as a research-and-calculate task very close to a written case. The full format is in the McKinsey test in 2026.
Materials for week 4
For the timed sets you need realistic, full-length tests with explained answers. The Prep Pack includes two full 26-question written-case practice tests (The Key to the PST and The Second Key to the PST) plus Cracking the Case for the interview rounds, at about 40% off the separate prices. The practice tests were designed for the PST, which is retired, and they fit week 4 of this plan exactly. See the Prep Pack. For broader planning across tests and interviews, read case interview preparation and how to beat a written case test.
Frequently asked questions
How long should I practice for a McKinsey online assessment?
Four weeks at about five hours per week is a good baseline for most candidates. Start earlier if mental math or English business reading is a weak point.
Is PST practice still relevant now that McKinsey uses Solve?
Yes, for the underlying skills. Solve uses games, but it rewards the same habits: filtering information, accurate math and structured reasoning under time pressure.
How many full practice tests should I take?
At least two full timed tests, with a complete review of each. When I coached PST candidates, two or three full tests were usually enough to feel confident.
What is the best way to practice mental math?
Short daily drills of 15 minutes: percentages, growth rates, ratios and multiplication of large numbers, done on paper without a calculator and checked afterward.