Let's say your interest rate is 8%. 72 ∕ 8 = 9, so it will take about 9 years to double your money. A 10% interest rate will double your investment in about 7 years (72 ∕ 10 = 7.2); an amount invested at a 12% interest rate will double in about 6 years (72 ∕ 12 = 6).
The time required for a sum to double itself at 8% per annum simple interest is 12.5 years.
For example, if an investment scheme promises an 8% annual compounded rate of return, it will take approximately nine years (72 / 8 = 9) to double the invested money.
A simple way to estimate the time it takes to double your money with compound interest is the Rule of 72. By dividing 72 by your annual interest rate, you get the approximate number of years needed to double your investment. With an 8% yield, it would take approximately nine years to double your money (72 / 8 = 9).
Is a rate of return of 8% a good average annual return? The answer is yes if you're investing in government bonds, which shouldn't be as risky as investing in stocks.
⇒T=1008=12.5 years. Q. In how many years will a sum of money double itself at 4% per annum ?
For example, if you want to double your money in eight years, divide 72 by eight. This tells you that you need an average annual return of 9% to double your money in that time.
For example, if you invest $10,000 at 10 percent compound interest, then the “Rule of 72” states that in 7.2 years you will have $20,000. You divide 72 by 10 percent to get the time it takes for your money to double. The “Rule of 72” is a rule of thumb that gives approximate results.
The time it takes to double a million dollars depends on the investment's annual growth rate. Using the Rule of 72 (72 divided by growth rate), it estimates the time. For instance, at a 7% annual return, it would take around 10 years to double to $2 million. Higher returns expedite growth.
The theme of the rule is to save your first crore in 7 years, then slash the time to 3 years for the second crore and just 2 years for the third! Setting an initial target of Rs 1 crore is a strategic move for several reasons.
For other compounding frequencies (such as monthly, weekly, or daily), prospective depositors should refer to the formula below. Hence, if a two-year savings account containing $1,000 pays a 6% interest rate compounded daily, it will grow to $1,127.49 at the end of two years.
Here's how it works: Divide 72 by your expected annual interest rate (as a percentage, not a decimal). The answer is roughly the number of years it will take for your money to double. For example, if your investment earns 4 percent a year, it would take about 72 / 4 = 18 years to double.
Here are the best low-risk investments in 2025:
High-yield savings accounts. Money market funds. Short-term certificates of deposit. Cash management accounts.
This rule is based on the principle of compounding interest and suggests that if you invest in a mutual fund with a 12 per cent annual return, your investment will double approximately every 8 years. After the first doubling, it will double again in the next 4 years, and then a final time in the subsequent 3 years.
One of those tools is known as the Rule 72. For example, let's say you have saved $50,000 and your 401(k) holdings historically has a rate of return of 8%. 72 divided by 8 equals 9 years until your investment is estimated to double to $100,000.
If you start with 1 dollar and double it every day for 30 days, you would have approximately $1,073,741,824. This shows the concept of exponential growth. Like the penny example, this is not typically possible in real-world investing scenarios.
Higher-risk investments like stocks have historically doubled money faster (around seven years) compared with lower-risk options like bonds (around 12 years). The rule provides an estimate, not a guarantee, since actual investment returns vary year to year.
To use the rule of 72, divide 72 by the fixed rate of return to get the rough number of years it will take for your initial investment to double. You would need to earn 10% per year to double your money in a little over seven years.
It will take 16 years for the sum of money to become five times.
Hence, R = 5%.