Rule of 72
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Annual Return
Quick mental math for compounding
How Rule of 72 Works
Years to Double = 72 ÷ Rate
Example: At 8% return, money doubles in 72÷8 = 9 years. Simple, fast, and surprisingly accurate for rates between 5-15%.
Years to Double Your Money
9.0
At 8% annual return, your money doubles in 9.0 years
Doubles in
9.0 yrs
Triples in
14.1 yrs
4x in
18.0 yrs
Compare Common Investments
See how long different instruments take to double your money
Savings Account
3.5% annual
20.6 yrs
Fixed Deposit
7% annual
10.3 yrs
PPF
7.1% annual
10.1 yrs
Inflation
6% annual
12.0 yrs
Equity MF (avg)
12% annual
6.0 yrs
Top Equity (10y)
15% annual
4.8 yrs
Insight
At 8% per year, ₹1 lakh becomes ₹2 lakh in 9.0 years, ₹4 lakh in 18.0 years, and ₹8 lakh in 27.0 years. That's exponential growth!
Pro Tip
- •Quick mental math for compound interest - super useful for investment planning.
- •Works best for rates between 5-15%. Below 5%, use Rule of 70 (more accurate).
- •Inflation @ 6% means prices double every 12 years - factor this into long-term plans.
- •The earlier you start investing, the more doublings you get in your lifetime.
What is Rule of 72?
The Rule of 72 is a simple mental math shortcut to estimate how long it takes for an investment to double at a given annual return rate. Just divide 72 by the rate and you get approximate years to double. It's accurate for rates between 5-15% and incredibly useful for quick investment decisions without a calculator.
How to Use
- 1Enter the annual return rate
- 2See years to double, triple, and quadruple
- 3Compare with common investment options
Formula
Years to Double = 72 ÷ Annual Return RateFrequently Asked Questions
72 is a convenient number with many divisors (2, 3, 4, 6, 8, 9, 12). It's mathematically derived from natural logarithm and gives accurate doubling time for typical investment returns.