The Rule of 72 (2024)

FAQs

The Rule of 72? ›

For example, the Rule of 72 states that $1 invested at an annual fixed interest rate of 10% would take 7.2 years ((72 ÷ 10) = 7.2) to grow to $2. In reality, a 10% investment will take 7.3 years to double (1.10^7.3 = 2). The Rule of 72 is reasonably accurate for low rates of return.

How Do You Calculate the Rule of 72? Here's how the Rule of 72 works. You take the number 72 and divide it by the investment's projected annual return. The result is the number of years, approximately, it'll take for your money to double.

Key Takeaways:

The rule of 72 can help you forecast how long it will take for your investments to double. Divide 72 by the annual fixed interest rate to determine the rate at which the money would double. Historical returns on your investment type can help choose a realistic expected return rate, in some cases.

The Rule of 72 is a calculation that estimates the number of years it takes to double your money at a specified rate of return. If, for example, your account earns 4 percent, divide 72 by 4 to get the number of years it will take for your money to double. In this case, 18 years.

Do you know the Rule of 72? It's an easy way to calculate just how long it's going to take for your money to double. Just take the number 72 and divide it by the interest rate you hope to earn. That number gives you the approximate number of years it will take for your investment to double.

So, if you have Rs 10 lakh right now, that would increase to around Rs 16 lakh over the next five years. Further, remember that you should invest at least one-third of your money in equity to enjoy inflation-adjusted income during retirement. Moreover, you must limit your withdrawals to 6 per cent of your corpus.

The Rule of 72 helps you determine how long it might take for your money to hypothetically double. It's worth noting, the “rule of 72” definition isn't necessarily perfectly accurate because past market results do not predict future market behavior.

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To turn $5,000 into more money, explore various investment avenues like the stock market, real estate or a high-yield savings account for lower-risk growth. Investing in a small business or startup could also provide significant returns if the business is successful.

Your investments

With an annual 4% return, it would take 18 years (72/4) to approximately double. With a 6% return, it would take 12 years (72/6), while with an 8% return it would take 9 years (72/8).

Does the Rule of 72 apply to debt? ›

You can also apply the Rule of 72 to debt for a sobering look at the impact of carrying a credit card balance. Assume a credit card balance of $10,000 at an interest rate of 17%. If you don't pay down the balance, the debt will double to $20,000 in approximately 4 years and 3 months.

1 At 10%, you could double your initial investment every seven years (72 divided by 10). In a less-risky investment such as bonds, which have averaged a return of about 5% to 6% over the same period, you could expect to double your money in about 12 years (72 divided by 6).

The rule of 8-4-3 when it comes to compounding indicates a style of investment that accelerates growth with time. Initially, a corpus doubles within 8 years through an average annual return of 12% subsequently another doubling happens for the same period after another 4 years following its initial setting up.

There are two things the Rule of 72 can tell you reasonably accurately: how many years it will take to double your money and what kind of return you will need to double your money in a fixed period of time.

Choice of rule

Since daily compounding is close enough to continuous compounding, for most purposes 69, 69.3 or 70 are better than 72 for daily compounding. For lower annual rates than those above, 69.3 would also be more accurate than 72. For higher annual rates, 78 is more accurate.

The rule of 72 is only an approximation that is accurate for a range of interest rate (from 6% to 10%). Outside that range the error will vary from 2.4% to 14.0%. It turns out that for every three percentage points away from 8% the value 72 could be adjusted by 1.

The Rule of 72 is a simple way to determine how long an investment will take to double given a fixed annual rate of interest. Dividing 72 by the annual rate of return gives investors a rough estimate of how many years it will take for the initial investment to duplicate itself.

The number of years it takes for a certain amount to double in value is equal to 72 divided by its annual rate of interest.

Rule of 72 Formula

You can calculate the number of years to double your investment at some known interest rate by solving for t: t = 72 ÷ R. You can also calculate the interest rate required to double your money within a known time frame by solving for R: R = 72 ÷ t.

Final answer:

It will take approximately 15.27 years to increase the $2,200 investment to $10,000 at an annual interest rate of 6.5%.