Rule of 72 Calculator
Years to double your money at any interest rate — the classic Rule of 72, plus exact math.
–Rule of 72 estimate
–Exact doubling time
–$10k becomes (in 20 yrs)
How to use
Enter an annual interest rate, then click Calculate.
Frequently asked questions
How accurate is the Rule of 72?
Within ~1% for rates between 6-10%. It drifts at very low or very high rates — the exact formula is shown too.
Does it work for debt too?
Yes — unfortunately. A 24% APR credit card balance doubles in about 3 years if unpaid.
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