Rule of 72 Calculator
How many years your money takes to double at a given return — or the return you need to double it in time.
Result
How to use
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Enter a yearly return to see how long your money takes to double.
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Or enter the number of years to see the return you need.
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Compare the quick Rule of 72 estimate with the exact answer.
Questions
What is the Rule of 72?
Divide 72 by the yearly return to estimate the years needed to double your money: at 8% it takes about 72 ÷ 8 = 9 years. Divide 72 by the years to get the return you need. It works best for returns between 6% and 10%.
How accurate is it?
Very close for normal returns. The exact time is ln(2) ÷ ln(1 + r). At 8% the exact answer is 9.01 years. For tripling use 114 and for 4× use 144.
Can I use it for inflation?
Yes. At 6% inflation prices double in about 12 years, so your money loses half its buying power in that time.
About this Rule of 72 tool
Rule of 72 Calculator — How many years your money takes to double at a given return — or the return you need to double it in time. It is one of 200 free tools on namasivayam.in, made by software engineer Namasivayam Vadivelan for everyday use in India.
Everything is calculated instantly in your browser: nothing you type or upload is sent to any server, there is no sign-up, and it works on mobile and desktop. Enter a yearly return to see how long your money takes to double.
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Results are estimates to help you plan. They are not financial, tax or medical advice.