Rule of 72 Calculator
How long until your money doubles? Ollie counts pebbles while you wait.
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A note on returns
The annual return you enter is a long-term planning assumption for diversified stock investments (like index funds) — a projection, not a guaranteed rate. For context: cash savings currently earn around 4%, while the stock market has averaged about 10% a year before inflation (roughly 7% after) over the past century. Actual returns vary year to year, and past performance never guarantees future results.
Rule of 72 FAQ
What is the Rule of 72?
It is a quick mental shortcut: divide 72 by your annual return to estimate how many years it takes your money to double.
Is the Rule of 72 exact?
It is a close approximation, most accurate for returns between 6% and 10%. For exact numbers use the compound interest calculator.
What return should I use?
A common long-term planning assumption for a diversified portfolio is 7% — not a guaranteed rate and not a bank deposit rate (cash savings currently earn around 4%). Historically stocks have averaged about 10% a year before inflation.