Compounding Rules
Key Takeaway
The Rule of 72 estimates doubling time: years = 72 / interest rate. At 12% returns, your money doubles every 6 years. At 8%, every 9 years. This mental math shortcut is invaluable for quick financial planning.
Rule of 72
Doubles your money
Rule of 114
Triples your money
Rule of 144
Quadruples your money
Milestone Purchasing Power Comparison
What to do next
Based on your Compounding Rules, here are the tools you should try next:
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The Heuristics of Wealth
You don't need a complex spreadsheet to do financial planning. The Rules of Compounding are mental math shortcuts that tell you exactly how long it takes to double, triple, or quadruple your money at a given interest rate.
Mental Math at the Dinner Table
- Use the **Rule of 72**: 72 / 6 = **12 years**.
What if you want it to triple to ₹30 Lakhs?
- Use the **Rule of 114**: 114 / 6 = **19 years**.
What if you invested that same ₹10 Lakhs in an index fund returning 12%?
- It doubles (₹20L) in: 72 / 12 = **6 years**.
- It triples (₹30L) in: 114 / 12 = **9.5 years**.
- It quadruples (₹40L) in: 144 / 12 = **12 years**.
By simply knowing these rules, you realize that in the same 12 years it takes the FD to double your money, the index fund would have quadrupled it.
The Rule of 72 and Other Compounding Shortcuts Every Investor Should Know
The Rule of 72 is one of finance's most useful mental shortcuts. Divide 72 by your annual return rate and you get the approximate number of years to double your money. At 12% return: 72/12 = 6 years to double. At 6%: 12 years. At 3% (savings account): 24 years.
This simple rule reveals why instrument selection matters so much. Money in a 3% savings account doubles every 24 years , meaning ₹10 lakhs becomes ₹20 lakhs in 24 years. Money in an equity fund at 12% doubles every 6 years , meaning ₹10 lakhs becomes ₹20 lakhs in 6 years, ₹40 lakhs in 12, ₹80 lakhs in 18, ₹1.6 crore in 24 years. Same time. Same money. Nine times more wealth.
The Rule of 114 tells you how long to triple your money (114/rate). The Rule of 144 for quadrupling. These are approximations but remarkably accurate for rates between 6–20%.
There's also the Rule of 70 (often used by economists for inflation): at 7% inflation, prices double in 10 years. This is why a ₹50,000 monthly expense today becomes ₹1 lakh/month in 10 years , a critical input for retirement planning that most people dramatically underestimate.
Frequently Asked Questions
What is the Rule of 72?
Divide 72 by your annual return rate to estimate how many years it takes to double your money. At 12% returns, money doubles in 72/12 = 6 years. At 8% returns, it takes 72/8 = 9 years.
What are Rules of 114 and 144?
Rule of 114: Divide 114 by your return rate to find years to triple your money. Rule of 144: Divide 144 by return rate to find years to quadruple. At 12%: Triple in 9.5 years, Quadruple in 12 years.
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