Rule of 72 Calculator illustration

Rule of 72 Calculator

Applies the rule of 72 — years to double ≈ 72 / rate — and compares it with the exact logarithmic answer, plus a cheat-sheet table for common rates.

Read the full guide to this tool

Notes

The rule is a mental-math approximation of ln(2)/ln(1+r); it is most accurate around 8%.
This is an educational estimate, not financial advice; talk to a qualified adviser before making money decisions.