Free tool
Rule of 72 calculator
Updated November 6, 2026. Runs entirely in your browser; nothing you type is sent anywhere.
Enter an annual percent return or a years-to-double target. You'll see the classic Rule of 72 sketch (72 ÷ rate ≈ years to double, or 72 ÷ years ≈ rate) plus one calm sentence you can adapt. This is arithmetic only—not investment advice, not a forecast, and not a substitute for a full compound-interest model.
How to use the number
- Treat it as a napkin sketch, then check a fuller model when the decision is real money.
- For contributions over time, use the free compound interest calculator.
- When the hard part is the raise, bill, or offer call that funds the savings rate, use a script.
What to say when cash or pay is the bottleneck
Knowing the doubling sketch is step one. Saying the next line on a bill, raise, or offer call is where people freeze. The Bills Kit ($19) gives word-for-word lines for bill moments plus Call Mode. If pay is the lever, see the Offer Kit ($29). One-time purchase, 14-day refund on both.
Get the Bills Kit, $19 Get the Offer Kit, $29
What is the Rule of 72?
A quick mental sketch: years to double ≈ 72 ÷ annual percent return. Example: 72 ÷ 8 ≈ 9 years to double at a steady 8% annual return. It is an approximation, not a precise compound-interest engine.
When is the Rule of 72 inaccurate?
It is rougher at very high or very low rates, with irregular contributions, fees, taxes, and variable returns. For a fuller future-value sketch, use the free compound interest calculator.
Is this investment advice?
No. It is simple arithmetic on the rate or years you enter, plus a sample sentence you can adapt. It is not a portfolio recommendation, tax advice, or a substitute for a qualified professional.
Can I solve for the rate instead of years?
Yes. Approximate annual percent return ≈ 72 ÷ years to double. This page flips either way from the numbers you type.
Guidance only, not legal, financial, or tax advice. The calculator does simple arithmetic on the numbers you enter.