Simple Interest VS Compound Interest

Simple Interest VS Compound Interest

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Author: Sarthak Bhalerao


Interest is a monetary charge levied on borrowed money and it is represented as an annual percentage rate. Interest is the amount of money the lender receives for lending out money. There are two types of interests: Simple Interest and Compound Interests. Let us look at both these types and what the differences are between the two.

Table of Contents

  1. What is Simple Interest?
  2. What is Compound Interest?
  3. Conclusion

What is Simple Interest?

Simple interest is as the name suggest an easy and simple method of calculating interest on the borrowed capital. In simple interest, the principal amount is always the same. When you make an interest payment, the payment goes towards that month’s interest and the remainder goes to the capital so that the interest never accrues. It is a benefit to the customer when they pay their simple interests on time or early every month. Auto loans, short term loans, mortgages are simple interest loans [1] [2].

The formula for simple interest and amount to be repaid:

S.I. = (P×N×R)/100                                         Amount = Principal + S.I.

P = Principal Amount

N = No. of years 

R = Rate of Interest

A = Amount (S.I. + Principal amount)

Let’s look at an example.

Bob takes a car loan of $18,000 with a 6% interest for 3 years. The simple interest would be 

=(P×N×R) / 100 = (18000×3×6) / 100 = $3240

 Total Amount to be repaid will be 18000 + 3240 = $21,240

What is Compound Interest?

Compound interest is the interest on a loan calculated Based on both the initial principal and the accumulated interests from previous periods. Unlike simple interest, the interest adds to the principal amount every year [3]. To give you a better understanding of this, consider that you have deposited ₹1000 in a bank at 10% interest. According to simple interest and compound interest, earnings for the first year would be 10% of 1000, that is ₹100. In simple interest, you will earn ₹100 in the second year as well. But in compound interest, the interest gets added to the principal amount each time. This means that the new principal amount is ₹1100. So, you would be getting 10% on ₹1100 as compared to ₹1000. So, your earnings in the second year would be ₹110.

Einstein once said that ‘Compounding is the world’s eighth Wonder!’ This is what he was talking about. Compound interest will make your sum grow at a much faster rate than simple interest. The rate at which the compound interest accrues differs on the frequency of compounding i.e., either monthly, quarterly, semi-annually or annually. This is because the interest-on-interest effect can generate more positive returns. 

The formula for Compound Interest for calculating the final amount [4]:

Amount  = Final Amount

P = Principal Value

R = Interest Rate

N = Number of times interest is applied per year

T = Total number of years. 

Let’s take the same example as taken in simple interest but this time Bob will be investing $18,000 in a bank at 6% interest given quarterly for 3 years. As the interest is paid quarterly, N = 4. The final amount would be

As you can see by the compounding effect, the final amount is $281 more than the Simple Interest amount.


The major difference between simple interest and compound interest is that in the simple interest the principal amount remains the same throughout the entire duration whereas in the compound interest the interest gets added to the principal amount every time. This drastically affects the final amount which one would get after the maturity period. These types of interests are widely used in many financial services for banking purposes. Loans such as car loans, educational loans, instalment loans use simple interest. The compounding interest is used by savings bank accounts, FDs, mutual funds etc.



“Simple Interest,” CueMath, [Online]. Available: [Accessed 17 September 2021].


A. Hayes, “Simple Interest,” Investopedia, 23 March 2021. [Online]. Available: [Accessed 17 September 2021].


J. Fernando, “Compound Interest,” Investopedia, 16 February 2021. [Online]. Available: [Accessed 17 September 2021].


“Compound Interest,” The Calculator Site, [Online]. Available:,the%20number%20of%20time%20periods.. [Accessed 17 September 2021].

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Sarthak Bhalerao

One comment

  1. In the beginning I was skeptical that I would be able to read such a long post. The way you write definitely attracted my attention. This was a great piece. Great Article Neil. While I did read it a few weeks ago, I did not make any comments. However , I felt that the article was good enough to merit a thankyou.

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