Doubling time Calculator

The time it takes for an amount to double in size at a constant growth rate is known as the doubling time.

Doubling Time Calculator

To get the doubling time for a constant growth rate, we have the Doubling Time Calculator. Use the free online tool to determine how long it will take for an amount to double in value given the growth rate per period.

What is the Doubling Time Formula?

The term “doubling time” refers to the period it will take for your investment to double in value at a specific interest rate. Rule of 70 is another name for this idea that is widely popular since it can be used to roughly calculate how long it will take for something to double. This will likewise produce a number that is very similar to that of the doubling formula. This idea is frequently used to compare investments with various interest rates and aids in our understanding of how rapidly an investment grows.

The following two methods will almost always get the same result when used to calculate doubling time:

Doubling Time \( = \dfrac{Ln (2)}{Ln (1+r)} \)


Ln – Natural Log

r – Interest Rate

Doubling Time \( = \dfrac{70}{r}\)

Use the absolute value of r rather than the decimal number in this formula. For instance, if r is provided at 5%, we shall utilize 5% rather than 0.05.


Example 1: An employee’s salary increases by 19% after every 6 months. An employee wants to find out how long it will take to double it. Calculate the doubling time?

\(= \dfrac{log(2)}{log(1+ increase)} \)

\( = \dfrac{log(2)}{ log(1+ \frac{19}{100})} \)

\(=\dfrac{log(2)}{log(1+ 0.19)}\)

\(= \dfrac{0.6931}{0.174} \)

\(=3.847\), which means there needs to have 4 increments to double the salary, it will need 2 years.


What distinguishes the rule of 70 formula from the rule of 72?

The rule of 70, which describes the doubling time, differs slightly from the rule of 72. The rule of 72 employs more whole numbers, which makes it much simpler to explain to customers who want to know how you are doubling their money.

In addition, rule 70 divides the interest rate by 70 rather than 72. Your preference will determine which formula will produce the same result.

How is the doubling time determined?

The following formula makes calculating the doubling time the easiest:


Doubling Time\( = \dfrac{70}{Interest \space Rate} \)


The \( \frac{growth}{interest \space rate} \space \) in this should be expressed as a full number rather than a decimal.

Why is the doubling time calculation important?

When comparing investments with various rates of return, the doubling time is frequently utilized. To make financial decisions, it is crucial to understand how money increases over time.

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