How fast can you double your money with PPF, MF, Bank FDs — Rule of 72 explains (2024)

FAQs

How long will it take to double your money using the Rule of 72? ›

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.

At 6% interest rate i.e. (72/6) it will take 12 years for your money to double. Similarly, At 9% interest rate, it would take eight years for your money to double. And, at 12% interest rate, it would take six years for your money to double.

Rule 72 is a method used to find the number of years an investment will take to double in value. In other words, this method is easy to calculate how long the invested amount will be doubled at a specific rate. This method provides an accurate measurement.

This means that the investment will take about 12 years to double with a 6% fixed annual interest rate. This calculator flips the 72 rule and shows what interest rate you would need to double your investment in a set number of years.

The Rule of 72 is reasonably accurate for low rates of return. The chart below compares the numbers given by the Rule of 72 and the actual number of years it takes an investment to double. Notice that although it gives an estimate, the Rule of 72 is less precise as rates of return increase.

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.

Errors and Adjustments

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.

It is not an exact value and can only provide a general estimate of the time required to double the investment. If the interest rate changes due to some factor, the Rule of 72 becomes null and void. The Rule of 72 does not apply to changing interest rate investments or basic interest investments.

t = ln(100,000/5,000)/0.097 ≈ 12.35 years Using the formula for continuous compounding interest, it will take approximately 12.35 years for a $5,000 investment to grow to $100,000 at an interest rate of 9.7% compounded continuously.

How much is $10000 for 5 years at 6 interest? ›

Summary: An investment of $10000 today invested at 6% for five years at simple interest will be $13,000.

Dividing these values gives us: t ≈ 0.6931/0.0583 ≈ 11.9 So, approximately, it would take around 11.9 years for the money to grow from $5,000 to $10,000 with a 6% interest rate.

The Rule of 70 Formula

Hence, the doubling time is simply 70 divided by the constant annual growth rate. For instance, consider a quantity that grows consistently at 5% annually. According to the Rule of 70, it will take 14 years (70/5) for the quantity to double.

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.

Therefore, we can calculate this by multiplying 1 by 2^19, which gives us 524,288. But since we need to reach $1,000,000, we need to continue doubling one more time. The 20th doubling brings us to a value of $1,048,576, which is greater than $1,000,000. So we know that it takes 19 doublings for $1 to reach $1,000,000.