Rule of 72 calculator
Quick estimate of how long an investment takes to double at a given annual rate — private in your browser.
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Quick answer
Years to double ≈ 72 ÷ rate (%). Example: 72 ÷ 8 ≈ 9 years at 8%. TryCalculatingNow runs the estimate locally — not investment advice.
Not financial or tax advice. Figures are mathematical illustrations only. Real products add fees, taxes, and terms that change the result — confirm with your bank, CA, or official notice. Numbers are not uploaded to our servers for processing.
Years to double (est.)
9.00
Frequently asked questions
What is the Rule of 72?
Years to double ≈ 72 ÷ annual interest rate (%). Example: at 8%, 72 ÷ 8 ≈ 9 years. It is a quick estimate, not exact compound math.
When is the Rule of 72 inaccurate?
It is closest for mid-single-digit rates. Very high or very low rates drift from true compound doubling time. Use the compound interest calculator for precise projections.
Are my numbers uploaded?
No. TryCalculatingNow runs the math in your browser after the page loads.