Rule of 72 Calculator
9 years
Your investment will double in approximately 9 years.
Please enter valid numbers greater than zero.
Rule of 72 Estimation
9 years
Your investment of $1,000 will double to $2,000
in approximately 9 years at 8% annual interest.
Compound Interest Calculation
$1,999.00
After 9 years, your investment will grow to exactly
$1,999.00 with annual compounding.
Growth Comparison
What is the Rule of 72?
The Rule of 72 estimates how long an investment takes to double: Years ≈ 72 ÷ Rate.
Example: 8% → 72 ÷ 8 = 9 years. It’s most accurate for ~6%–10% rates.