Rule of 72 Calculator

Use this free Rule of 72 calculator to find out roughly how many years it takes for money to double at a given yearly rate. Enter a starting amount and a yearly rate. The calculator shows the Rule of 72 estimate, the exact time, and how long it takes to grow four, eight or ten times.

What is the Rule of 72?

The Rule of 72 is a quick mental shortcut: divide 72 by the yearly rate to estimate the years needed to double your money. At 12% a year, 72 ÷ 12 gives 6 years. The exact figure, which this calculator also shows, is slightly longer at about 6.1 years. The rule works best for rates between about 6% and 10%, and drifts away from the true answer at very high or very low rates.

How this calculator works

The calculator uses the exact compounding formula, so the table shows when your money reaches 2, 4, 8 and 16 times its starting value, as long as that happens within 100 years. At a steady rate, each doubling takes the same number of years. For example, ₹1,00,000 at 12% becomes ₹2,00,000 in about 6.1 years, ₹4,00,000 in about 12.2 years and ₹8,00,000 in about 18.3 years. The result is an illustration, not a forecast.

Two ways to use it

Use it for returns, to see how long an investment may take to double. Use it for inflation too: at 6% inflation, prices double in about 12 years, which means the buying power of your money halves in that time.

What this calculator does not include

Taxes, costs and the ups and downs of real markets are not included. The calculator assumes a steady rate every year, with no money added or withdrawn. If you invest every month, use our SIP calculator instead.

Frequently asked questions

Is the Rule of 72 accurate?

It is a good approximation for moderate rates, and the calculator shows the exact figure beside it. For very high or very low rates the shortcut drifts away from the true answer.

Can I use it for inflation?

Yes. Enter the inflation rate and the result shows how long prices take to double. See what rising prices do to your own expenses with our Inflation calculator.

Is the return shown guaranteed?

No. The rate you enter is an assumption, not a promise. Mutual fund returns are market-linked and can be higher or lower. Mutual fund investments are subject to market risks. Read all scheme related documents carefully. Learn more on the AMFI investor awareness site.

What if I invest every month instead of once?

Try our SIP calculator for monthly investing, or our Lumpsum calculator for a one-time investment.