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Investor's Mental Math : CAGR, Lump sum compounding & More
Last updated 6/2026
English

What you'll learn

  • Apply the Rule of 72 to find doubling time for any return rate in seconds
  • Run the Rule of 72 in reverse to find the return rate needed to meet a goal
  • Convert any cumulative return percentage into a CAGR using the 4-step method
  • Compare investments of different ages fairly using annual return rates
  • Project a lump sum investment forward across decades using the doubling chain
  • Calculate how much to invest today to reach any future wealth target
  • Apply the Rule of 72 to inflation to find purchasing power halving time
  • Identify implausible return claims and fraudulent schemes using mental math
  • Read the rate-and-time grid and develop intuition for compounding outcomes
  • Apply all three tools together on a single investor decision using a structured checklist

Course content

11 sections11 lectures1h 40m total length
  • Introduction6:47

Requirements

  • Basic arithmetic (addition, division)
  • No financial background needed
  • No calculator or spreadsheet
  • Curiosity about how investments grow

Description

When a fund brochure says "450% returns since inception," most investors are impressed. But what does that number actually mean per year? The answer — approximately 9% — is something every investor should be able to calculate on the spot. This course gives you that ability.

The Compounding Code teaches three mental math frameworks that work together to help you evaluate any investment in under 30 seconds — without a spreadsheet, app, or calculator.

What you'll learn to do:

→ Find the doubling time of any investment in 2 seconds using the Rule of 72

→ Convert any cumulative return to an annual rate in under 20 seconds using the 4-step CAGR method

→ Project any lump sum investment forward — and reverse the calculation to find how much you need today

→ Spot fraudulent investment schemes using a single division

→ Understand why a 6% return difference can produce a 5× wealth difference over 30 years

These methods have been taught to first-time SIP investors, CA aspirants, and portfolio managers. The course includes 11 videos, 130+ minutes of content, and dozens of worked examples and practice questions — all grounded in real Indian investment scenarios (mutual funds, FDs, property, indices).

No financial background required. No calculator required. Just a willingness to think before you invest.

Who this course is for:

  • First-time and retail investors
  • CA and finance exam aspirants
  • SIP and mutual fund investors
  • Anyone who reads fund brochures