Estimate how long it takes to double money.
Please do not make financial decisions based on these results.
What is the Rule of 72 Calculator?
Estimate how long it takes to double money. To use the Rule of 72 Calculator, enter annual return; it returns years to double (rule of 72), exact years to double, years to triple (rule of 114), and shows them instantly as you type.
Where the Rule of 72 Calculator fits
Estimate how long it takes to double money. The main figure it returns is the Years to double (rule of 72), worked out from the values you enter.
It belongs with the other retirement tools. If you are comparing options or checking a result from another angle, try the Pension Calculator, Retirement Calculator or the Social Security Calculator.
How to use the Rule of 72 Calculator
- Fill in the fields. You will need Annual return (%). Use today’s balances and your real contribution amounts, then test a more cautious return. Fields marked optional can stay at zero.
- Read the result. The highlighted box gives the Years to double (rule of 72), and the cards below show Exact years to double, Years to triple (rule of 114). Tables and charts break it down further.
- Test other scenarios. Results update as you type. Change one value at a time to see what drives the answer, and press Reset to go back to the defaults.
Formula and how it works
Example with real numbers
Here is the Rule of 72 Calculator using the default values shown in the calculator above:
Inputs
| Annual return (%) | 7 |
|---|
Results
| Years to double (rule of 72) | 10.29 years |
|---|---|
| Exact years to double | 10.24 years |
| Years to triple (rule of 114) | 16.29 years |
With these inputs the calculator returns Years to double (rule of 72): 10.29 years. Change any value in the calculator to see how the result moves.
What if you change one input?
Sensitivity check: raising Annual return (%) from 7 to 8.4 (about 20% higher) and leaving everything else as in the example above changes the results like this:
| Result | Example | After the change | Change |
|---|---|---|---|
| Years to double (rule of 72) | 10.29 years | 8.57 years | -16.7% |
| Exact years to double | 10.24 years | 8.59 years | -16.1% |
| Years to triple (rule of 114) | 16.29 years | 13.57 years | -16.7% |
The input that moves the result most is the one to check twice. Change it in the calculator above to test your own case.
What the results tell you
The results panel of the Rule of 72 Calculator reports Years to double (rule of 72), exact years to double and years to triple (rule of 114). Compare these figures while changing one input at a time, and use the related calculators below to look at the same situation from another angle.
Method and limits. This calculator applies the formula in the section above to your inputs, in your browser; nothing you enter is stored on our servers. Retirement results depend on returns, inflation and contribution limits that change over time. They are projections, not promises. It is for information, not financial, tax or legal advice.
Frequently asked questions
How accurate is the rule of 72?
Very accurate for returns between 6% and 10%.
How much should I save for retirement?
Many planners suggest saving 10% to 15% of income, including employer match, starting early. The retirement calculator shows the monthly amount you need for your own goal.
When should I claim Social Security?
Claiming at 62 reduces your benefit permanently, while waiting until 70 increases it. The best age depends on your health, other income and spouse. The Social Security Calculator compares the options.
Are the results guaranteed?
No. Results depend entirely on the numbers you enter and the formulas shown on this page. Please do not make financial decisions based on them alone; confirm important figures with a licensed professional.
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