What you provide
What you provide
- Illustrative starting balance: Optional balance used to show the corresponding doubled amount.
- Annual growth rate: Positive annual compound rate used for both time estimates.
INVESTING / DOUBLING ESTIMATE
Rule of 72 Calculator
Estimate how many years a balance may take to double at a constant annual percentage rate and compare the mental shortcut with exact compounding.
- 01 Calculated in this tab
- 02 Values stay in this browser tab
- 03 Use boundary
Use boundary
Calculation path
The shortcut divides 72 by the entered percentage rate, while the exact comparison uses logarithms with annual compounding and the balance only illustrates the doubled amount.
Calculation path
Rule-of-72 years = 72 / annual percentage rate; exact years = ln(2) / ln(1 + rate).
What you receive
What you receive
- Rule-of-72 doubling estimate
- Exact annual-compounding time
- Illustrative doubled balance and approximation difference
Use boundary
Choose the maximum decimal places shown. This does not increase source accuracy.
The shortcut is most useful for moderate positive rates and does not model contributions, withdrawals, fees, taxes, or variable returns.
This calculator is an educational scenario model, not investment, tax, accounting, or valuation advice. Confirm definitions, timing, and decisions with source documents and a qualified professional.