Simple Interest and Compound Interest Basics (2024)

We hear about it all the time. There are few things in the financial world that are givens but even in the most uncertain environment, interest or in terms of stocks, dividends are one of those income streams that make us feel good. Often seen as unchanging, nearly all consumers understand interest because they often pay it on their loans or they earn it in their savings accounts.

If you’ve ever applied for a car loan, one of the items you look at first is the interest rate. We all understand that the higher the interest rate, the more money we will pay in the end but let’s look at a few other facts about interest rates that you may not know.

Simple Interest is Not as Simple as You Think

Simple interest is the easiest type of interest to understand. If you loaned a buddy $100 and told him that when he pays you back, he has to pay you $106, you charged him 6% on the loan. In finance terms, simple interest is calculated by multiplying the principal amount (100) times the rate (6%) times the amount of time (let’s say 1 year) 100 X .06 X 1 = $6. Pretty easy.

Banks are much more savvy than that, though. They aren’t going to give you $10,000 for a car and charge you 6% each year spread equally between interest and principal. They front load the interest in case you pay the $10,000 off early. If you looked at the amortization table that came with your loan documents you noticed that more interested is factored in to the first few years of the loan and as you reach the end, it becomes almost all principal.

This is far from “simple” and if you saw the calculations, you would agree. If you didn’t know what an amortization table was before now, just remember that it lays out how your total payment is broken down. If you want to see how interest is frontloaded in your loan, you can create your own amortization table by going to www.amortization-calc.com.

If you own certain fixed income investments the interest being paid to you is paid using a simple interest formula. You can reinvest your dividends (called the coupon) if you would like but it’s not compounded within the investment itself.

Compound Interest is Simpler than You Think

Compound interest is more difficult to calculate and for most of our purposes, the way it is calculated isn’t overly important. Since there is a seemingly endless supply of compound interest calculators, we won’t worry about the particulars but here’s what you need to know when you’re shopping around: Unless you’re working with six figure numbers, the type of compounding is unimportant. Let’s look at an example:

I found a compound interest rate calculator at webmath.com and came up with these figures:

Let’s say that you have $50,000 in a 1 year Guaranteed Investment Certificate at 5% interest that is compounded monthly. After one year you will have in your account $52,558.09.

Now, let’s say that you have that money in a GIC from a different bank but the interest is compounded daily. After one year you will have in your account $52,563.37.

Although many unknowing consumers find themselves comparing the different types of compounding, in reality, it makes very little difference. Some may argue that if you’re investing in GICs for 30 years that $5 difference adds up. It’s true. Over 30 years that would be about $674 but once 30 years of inflation eats in to it, that $674 is far less impressive.

Look at the “Y” Instead of the “R”

When comparing loan rates, don’t look at the APR. The APR or annual percentage rate is the amount of money you would pay or receive if the interest was calculated using simple interest. Since the APR doesn’t account for any compounding, look at the APY or annual percentage yield. The APY takes into account the type of compounding used.

For example, if a car dealership offered to finance a $10,000 loan at a 5% APR, you could go to another dealership and get the same APR but pay those couple of dollars more per year because of the compounding. A $10,000 loan at 5% compounded daily has an APY of 5.13% but if it is compounded monthly the APY is 5.12%. (By the way, the difference annually is all of $1.05)

Don’t Count on Compounding

If you’re investing, there’s no doubt that when you reinvest your returns over time, compounding does wonders for your portfolio. You can’t live on your RRSP contribution alone for your entire retirement so you have to rely on compounding to grow your nest egg.

However, you can’t use compounding as an excuse to not take an active part in the management of your retirement plan. If the world markets have another meltdown, compounding isn’t going to save you if you’re close to retirement. Make sure you have a qualified and more importantly, approachable investment advisor.

Tom Drake

Tom Drake is the owner and head writer of the award-winning MapleMoney. With a career as a Financial Analyst and over a decade writing about personal finance, Tom has the knowledge to help you get control of your money and make it work for you.

View all posts by Tom Drake

Simple Interest and Compound Interest Basics (1)

Simple Interest and Compound Interest Basics (2024)

FAQs

Simple Interest and Compound Interest Basics? ›

Simple interest is calculated on the principal, or original, amount of a loan. Compound interest is calculated on the principal amount and the accumulated interest of previous periods, and thus can be regarded as “interest on interest.”

How to know when to use simple or compound interest? ›

Which Is Better, Simple or Compound Interest? It depends on whether you're saving or borrowing. Compound interest is better for you if you're saving money in a bank account or being repaid for a loan. If you're borrowing money, you'll pay less over time with simple interest.

What are the basics of simple interest? ›

Simple Interest is calculated using the following formula: SI = P × R × T, where P = Principal, R = Rate of Interest, and T = Time period. Here, the rate is given in percentage (r%) is written as r/100. And the principal is the sum of money that remains constant for every year in the case of simple interest.

What is the basics of compound interest? ›

Compound interest is the interest calculated on the principal and the interest accumulated over the previous period. It is different from simple interest, where interest is not added to the principal while calculating the interest during the next period. In Mathematics, compound interest is usually denoted by C.I.

What are the formulas for simple interest and compound interest? ›

Interest Formulas for SI and CI
Formulas for Interests (Simple and Compound)
SI FormulaS.I. = Principal × Rate × Time
CI FormulaC.I. = Principal (1 + Rate)Time − Principal

What is compound vs simple interest for dummies? ›

Simple interest is calculated on the principal, or original, amount of a loan. Compound interest is calculated on the principal amount and the accumulated interest of previous periods, and thus can be regarded as “interest on interest.”

Is a home loan simple or compound interest? ›

The important thing to note for Home Loan interest rate is that it is compounded interest and not simple interest. In other words, you don't pay interest only on the principal amount, but you pay interest on the principal amount plus the interest accrued.

How do you explain simple interest to a child? ›

When the fee charged for borrowing money is a fixed yearly percentage of the amount borrowed, it is called simple interest. The amount borrowed is called the principal, or the present value of the transaction. The amount owed at the end of the lending period is known as the future value of the principal.

What is the simple interest on $8000 for 4 years at 2% per annum? ›

Answer. So, the simple interest on 8000 naira for 4 years at a rate of 2% per annum is 160 naira.

How to calculate compound interest? ›

Compound interest is calculated by multiplying the initial loan amount, or principal, by one plus the annual interest rate raised to the number of compound periods minus one. This will leave you with the total sum of the loan, including compound interest.

How to explain compound interest to a child? ›

Put simply, compound interest is when you earn interest on both the money you've saved and the interest you've already earned.

How do you explain compound interest with examples? ›

For example, if you deposit $1,000 in an account that pays 1 percent annual interest, you'd earn $10 in interest after a year. Thanks to compound interest, in Year Two you'd earn 1 percent on $1,010 — the principal plus the interest, or $10.10 in interest payouts for the year.

What is an example of a simple interest? ›

"Simple" interest refers to the straightforward crediting of cash flows associated with some investment or deposit. For instance, 1% annual simple interest would credit $1 for every $100 invested, year after year.

How to solve simple interest problems? ›

The simple interest formula is given by I = PRt where I = interest, P = principal, R = rate, and t = time. Here, I = 10,000 * 0.09 * 5 = $4,500. The total repayment amount is the interest plus the principal, so $4,500 + $10,000 = $14,500 total repayment.

What is the magic of compound interest? ›

When you invest, your account earns compound interest. This means, not only will you earn money on the principal amount in your account, but you will also earn interest on the accrued interest you've already earned.

When should you use compound interest? ›

When it comes to investing, compound interest is better since it allows funds to grow at a faster rate than they would in an account with a simple interest rate. Compound interest comes into play when you're calculating the annual percentage yield. That's the annual rate of return or the annual cost of borrowing money.

What type of loans use compound interest? ›

Compounding doesn't only happen on accounts that make you money. Credit cards, student loans and mortgages can use compound interest to determine how much you end up paying. We'll look at an example of this below.

Why would an individual prefer compound interest over simple interest? ›

Why is compound interest important? Compound interest causes your wealth to grow faster. It makes a sum of money grow at a faster rate than simple interest because you will earn returns on the money you invest, as well as on returns at the end of every compounding period.

How to solve difference between simple interest and compound interest? ›

Detailed Solution
  1. Given: Rate of Interest = 20% per annum. Time = 2 years. ...
  2. Formula Used: The difference between compound interest and simple interest. obtained on Rs. ...
  3. Calculation: Difference in Simple Interest and Compound Interest for 2 years = P(R/100)2 ...
  4. ∴ The sum is Rs. 15,625.
  5. Alternate Method. CI = P × [(1 + R/100)n - 1]

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