Rule of 72 Calculator
Use the Rule of 72 to quickly estimate how many years it will take to double your investment based on your annual return. Simple compound interest shortcut.
The Rule of 72 Calculator
The fastest way to estimate how long it takes to double your money.
What is the "Rule of 72"?
It's a simplified mental shortcut used to estimate the impact of compound interest. Just divide 72 by your annual return to see the years needed to double.
Accuracy Comparison
Investor Insight: At a 10% return, your money doubles every 7.2 years. Over a 30-year career, that's roughly 4 "doublings."
What is the Rule of 72?
The Rule of 72 is a simple mathematical mental shortcut used to estimate the impact of compound interest. It provides a quick answer to one of the most common questions in personal finance: "How long will it take for my money to double?"
The Simple Formula
To find the number of years required to double your investment, you simply divide 72 by your expected annual rate of return.
Examples of the Rule of 72 in Action
Depending on where you put your money, the doubling speed varies drastically:
- Standard Savings Account (0.5%): It would take 144 years to double.
- High-Yield Savings (4.5%): It would take 16 years to double.
- S&P 500 Historical Average (10%): It would take just 7.2 years to double.
- Aggressive Growth Stock (15%): It would take 4.8 years to double.
Is the Rule of 72 Accurate?
While the "Rule of 72" is a simplification, it is remarkably accurate for most standard interest rates (between 5% and 20%). Our calculator also provides the "Precise Math" output using logarithmic calculations to show you exactly how close the estimate really is.
The 'Rule of 72' vs 'Rule of 114'
Did you know there are other rules? If you want to know how long it takes to triple your money, use the Rule of 114. If you want to know how long to quadruple your money, use the Rule of 144.
The tools and calculators provided on The Simple Toolbox are intended for educational and informational purposes only. They do not constitute financial, legal, tax, or professional advice. While we strive to keep calculations accurate, numbers are based on user inputs and standard assumptions that may not apply to your specific situation. Always consult with a certified professional (such as a CPA, financial advisor, or attorney) before making significant financial or business decisions.
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