How to use this calculator
- Enter annual effective growth rate (%).
- Choose a display currency, then select Calculate. Results also update after a brief pause while you edit.
- Read the result with the assumptions below. Export details or save a second scenario to compare your choices.
Formula and method
Approximation=72/rate%; exact time=ln(2)/ln(1+effective rate).
Assumptions and limitations
Requires a positive constant return and no cash flows, tax or fees; no market-return prediction.
Worked example
With annual effective growth rate (%) = 6, rule of 72 estimate in years is approximately 12.
What the result means
Compare a mental shortcut with the exact constant annual-compounding solution.
Common questions
How should I interpret rule of 72 estimate in years?
Compare a mental shortcut with the exact constant annual-compounding solution.
What should I check before using this result?
Requires a positive constant return and no cash flows, tax or fees; no market-return prediction.
Methodology and transparency
Calculation specification reviewed on 2026-10-14. Mathematical implementation is tested against independent reference fixtures. This does not imply review by a licensed financial professional. Read the testing and precision policy.