Rule of 72
Years to double at a given rate.
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Divide 72 by an annual percent to estimate years to double. A second line shows the compound-interest estimate for comparison.
How to use this tool
- Enter the amounts. Fill in principal, rate, term, or prices. Use the same currency throughout.
- Read the estimate. The figures are a simplified model, not a lender or tax quote.
- Compare a related tool. Open amortization, compound interest, or paycheck if you need another view.
When it drifts
The shortcut is rougher at very high or very low rates. It ignores taxes, fees, and changing yields.
Frequently asked
Why 72 and not 69 or 70?
72 divides evenly by many whole rates. It is a teaching shortcut.
Does this pick an investment?
No.
Can I solve for the rate instead?
Yes. Enter years to double and read the implied rate estimate.
Is the rule of 72 a substitute for a plan?
No. It is a doubling-time estimate, not financial advice.
What about monthly compounding?
The precise line can use monthly compounding. The 72 shortcut stays annual.