Growth Rates and CAGR Mental Math
Fast methods to estimate growth rates and CAGR during finance and consulting interviews.
Last reviewed: 2026-03-04
Quick Answer
For small intervals, estimate annualized growth with rules of thumb first, then refine using logarithm-free approximations when needed.
Why It Matters in Interviews
- Growth framing appears in revenue and market analysis cases.
- CAGR mental math separates prepared candidates from average ones.
- Approximation-first thinking keeps answers quick and defensible.
Practice Drill Plan
- Practice YoY, MoM, and multi-year growth conversions.
- Run 10 CAGR approximations with answer bounds.
- Pair each estimate with a one-sentence interpretation.
Common Mistakes
- Confusing percentage-point changes with percent changes.
- Using exact compounding math when estimate is sufficient.
- Forgetting to state timeframe clearly.
Practice Now
Use these drills in short sessions and track your score/accuracy trend each week.