What is interest?

Interest is the cost of using somebody else’s money. When you borrow money, you pay interest. When you lend money, you earn interest.

Here, you’ll learn more about interest, including what it is and how to calculate how much you either earn or owe depending on whether you lend or borrow money.

What is interest?

Interest is calculated as a percentage of a loan (or deposit) balance, paid to the lender periodically for the privilege of using their money. The amount is usually quoted as an annual rate, but interest can be calculated for periods that are longer or shorter than one year.

Interest is additional money that must be repaid in addition to the original loan balance or deposit. To put it another way, consider the question: What does it take to borrow money? The answer: More money.

How does interest work?

There are several different ways to calculate interest, and some methods are more beneficial for lenders. The decision to pay interest depends on what you get in return, and the decision to earn interest depends on the alternative options available for investing your money.

When borrowing: To borrow money, you’ll need to repay what you borrow. In addition, to compensate the lender for the risk of lending to you (and their inability to use the money anywhere else while you use it), you need to repay more than you borrowed.

When lending: If you have extra money available, you can lend it out yourself or deposit the funds in a savings account, effectively letting the bank lend it out or invest the funds. In exchange, you’ll expect to earn interest. If you are not going to earn anything, you might be tempted to spend the money instead, because there’s little benefit to waiting.

How much do you pay or earn in interest?

It depends on:

The interest rate

The amount of the loan

How long it takes to repay

A higher rate or a longer-term loan results in the borrower paying more.

Example: An interest rate of 5 percent per year and a balance of US$100 results in interest charges of US$5 per year assuming you use simple interest.

Most banks and credit card issuers do not use simple interest. Instead, interest compounds, resulting in interest amounts that grow more quickly.

How do I earn interest?

You earn interest when you lend money or deposit funds into an interest-bearing bank account such as a savings account or a certificate of deposit (CD). Banks do the lending for you: They use your money to offer loans to other customers and make other investments, and they pass a portion of that revenue to you in the form of interest.

Periodically, (every month or quarter, for example) the bank pays interest on your savings. You’ll see a transaction for the interest payment, and you’ll notice that your account balance increases.

You can either spend that money or keep it in the account so it continues to earn interest. Your savings can really build momentum when you leave the interest in your account; you’ll earn interest on your original deposit as well as the interest added to your account.

Earning interest on top of the interest you earned previously is known as compound interest.

Example: You deposit $1 000 in a savings account that pays a 5 percent interest rate. With simple interest, you’d earn US$50 over one year.

Account balance after one year = US$1 050.However, most banks calculate your interest earnings every day, not just after one year. This works out in your favour because you take advantage of compounding. Assuming your bank compounds interest daily:

Your account balance would be US$1 051,16 after one year.

The difference might seem small, but we’re only talking about your first $1,000. With every US$1 000, you’ll earn a bit more. As time passes, and as you deposit more, the process will continue to snowball into bigger and bigger earnings. If you leave the account alone, you’ll earn US$53,78 in the following year, compared to US$51,16 the first year. – The Balance.