The Rule of 72 is a quick mental math shortcut used to estimate how long an investment may take to double.
How it works
Divide 72 by the annual rate of return to estimate the number of years needed to double.
Example rates
At 6%, money may double in about 12 years. At 8%, it may double in about 9 years.
Best use
It is useful for quick estimates, not precise forecasts.
Limits
Actual investment returns vary, and taxes, fees, and inflation can change real results.
Why it is helpful
The rule shows how powerful time and return rate can be in long-term planning.
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Use the free Moniply rule of 72 calculator to turn this guide into numbers you can act on.
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Using the Rule of 72, 72 divided by 9% equals 8. That suggests money may double in about 8 years at a 9% annual return.
Frequently asked questions
Is the Rule of 72 exact?
No. It is an estimate, but it is useful for quick planning.
Can it be used for inflation?
Yes. It can estimate how long prices may take to double at a given inflation rate.
Does it include taxes and fees?
No. It is a simple estimate before taxes, fees, and real-world changes.
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Moniply provides educational content and calculator estimates only. This page is not financial, investment, tax, or legal advice. Consider your personal situation and consult a qualified professional where needed.