Rule of 72 at 3%: How Long to Double $100,000?
At a 3% annual return, money doubles approximately every 24 years (72 ÷ 3), so $100,000 becomes $200,000 in about 24 years.
How to use this tool
- Enter annual return rate, starting amount and projection years in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your years to double (rule of 72) and the full breakdown beneath it.
Savings accounts and bonds earning 3% show slower doubling — discover just how long it takes with the Rule of 72 starting at $100,000.
Frequently asked questions
- How accurate is the Rule of 72?
- It's a good approximation for rates between 6% and 10%. For exact doubling time, use ln(2) / ln(1 + r) ≈ 0.693 / r.
- Does it work for debt too?
- Yes — at 18% APR your credit card debt doubles in roughly 4 years if you make no payments. The rule is a powerful reminder of compounding in reverse.