Interest is one of those financial words that appears almost everywhere. You may see it when opening a savings account, applying for a car loan, reading a credit card statement, or making student loan payments.
Still, many people were never taught what interest actually means. You may know that a lower interest rate sounds good on a loan or that a higher rate could help your savings, but understanding what happens behind those numbers can feel confusing.
The good news is that you do not need to be a math expert to understand interest. It starts with one simple idea:
Interest is extra money connected to borrowing or saving money over time.
When you borrow money, interest is usually an additional amount you pay. When you keep money in an eligible savings account, interest is money you may earn. Once you understand those two sides, terms like APR, APY, principal, and compound interest become much easier to follow.
What Is Interest?
Imagine that a friend lends you $100. They tell you that you can repay them next month, but you need to give them $105.
The original $100 is the amount you borrowed. The additional $5 is interest. It is the cost of using your friend’s money for a month.
Now imagine putting $100 into an interest-earning savings account. After some time passes, your balance grows to $103. The original $100 is your deposit, and the additional $3 is interest you earned.
This is the main difference to remember:
Borrowing money may cause you to pay interest. Saving money may allow you to earn interest.
A Few Interest Terms You Will See
Before looking at loans and savings accounts, it helps to understand a few common words.
- The principal is the starting amount of money you borrow or deposit. If you borrow $10,000 to purchase a car, your starting principal is $10,000. If you deposit $1,000 into a certificate of deposit, your starting principal is $1,000.
- Your balance is the amount currently in the account or the amount you still owe. A loan balance usually gets smaller as you make payments. A savings balance can grow as you add money and earn interest.
- The interest rate is the percentage used to help calculate how much interest you pay or earn. For example, 5% of $100 is $5. However, that does not mean every loan or savings account with a 5% rate will add exactly $5 for every $100. The result also depends on how long the money is borrowed or saved, how payments are made, how often interest is calculated, and any fees connected to the account.
- The term is the length of time connected to the agreement. A car loan may have a 48-month or 60-month term. A certificate of deposit may have a six-month, one-year, or longer term.
- Your payment is the amount you are expected to pay toward a loan or credit card. A loan payment may include part of the original amount you borrowed, interest, and other costs.
Understanding these terms can help you look beyond the monthly payment and see the full cost of borrowing.
APR and APY: What Is the Difference?
APR and APY sound similar, but they are used for different sides of interest. APR, or Annual Percentage Rate, is commonly used when talking about borrowing. You may see an APR when comparing credit cards, auto loans, personal loans, and home loans. APR helps show the yearly cost of borrowing. Depending on the product, it may include the interest rate and certain fees. This makes APR a useful number when comparing similar loan offers. In general, a lower APR means borrowing will cost less, assuming the loan amount, fees, and repayment term are similar.
APY, or Annual Percentage Yield, is commonly used when talking about savings. You may see an APY on savings accounts, money market accounts, and certificates of deposit. APY shows how much your money could earn over one year and includes the effect of compounding. In general, a higher APY can help your savings grow faster, assuming the account requirements and fees are similar.
An easy way to remember the difference is:
APR helps you understand what borrowing may cost. APY helps you understand what saving may earn.
At a credit union, you may also see the word dividend. A dividend is money the credit union pays members on eligible deposit balances. You can still use APY when comparing the potential earnings of different accounts.
How Interest Helps Your Savings Grow
When you keep money in an interest-earning account, your financial institution may add money to your balance.
How much you earn depends on several things, including your balance, the account’s APY, how long the money remains in the account, account requirements, fees, and how often interest is compounded.
Here is a simplified example.
Imagine depositing $1,000 into an account that grows by 5% each year. This example is only meant to explain how growth works and does not represent a current Zing rate.
After the first year, the account earns approximately $50**, bringing the balance to $1,050.
During the second year, growth is calculated using the new balance of $1,050**. That means the account earns approximately $52.50 instead of another $50. The balance becomes $1,102.50**.
During the third year, the balance earns approximately $55.13. At the end of three years, the account has grown to approximately $1,157.63**.
The account earned a little more each year because previously earned interest became part of the balance. That is known as compound interest.
What Is Compound Interest?
Compound interest means your money may earn interest, and then the interest that was added can begin earning interest too. You can picture it like a snowball rolling downhill. It starts small, but as it rolls, it collects more snow. Once it becomes larger, it can collect even more. Savings can grow in a similar way. You start with your original deposit. Interest is added to it. The new, larger balance may then earn additional interest. Time plays a major role in compounding. The longer money remains in an eligible interest-earning account, the more opportunities it has to grow. This is one reason starting with a small amount can still be valuable. You do not need to wait until you have thousands of dollars saved. Consistent deposits and time can help build momentum.
How Interest Works on a Loan
When you take out a loan, a lender gives you money upfront. You agree to repay that amount over a certain period of time. Your payments generally go toward two main parts. One part reduces the principal, which is the amount you borrowed. The other part pays interest, which is the cost of borrowing the money. Some loan payments may also include fees, insurance, taxes, or other costs.
Here is an example of how an interest rate can change the cost of a car loan.
Imagine two people each borrow $15,000 and choose a 48-month repayment term. One person receives a 5% APR*. The other receives a 9% APR*.
With the 5% APR*, the monthly payment would be approximately $345. Over the full loan term, the borrower would pay approximately $1,581 in interest.
With the 9% APR*, the monthly payment would be approximately $373. Over the same term, the borrower would pay approximately $2,917 in interest.
That is a difference of about $28 each month and approximately $1,336 over the life of the loan.
The vehicle price did not change. The amount borrowed did not change. The repayment term did not change. The interest rate changed the total cost.
These are rounded educational estimates. Actual payments and costs depend on the loan agreement, fees, payment dates, credit history, collateral, and other factors.
Why Do People Receive Different Interest Rates?
Two people can apply to borrow the same amount and receive different offers. Lenders may review a person’s credit history, credit score, income, existing debts, loan amount, down payment, repayment term, and the type of property being financed. Current market conditions and the lender’s guidelines can also affect the offer. A stronger credit history may help someone qualify for a lower rate. A larger down payment may also reduce the lender’s risk. Someone who is freshly graduated or new to credit may have a limited credit history. That does not automatically mean they have handled money poorly. It may simply mean lenders have less information available to review. Building credit takes time. Making payments by the due date, keeping credit card balances manageable, and reviewing credit reports for mistakes can help create a stronger credit history.
How Credit Card Interest Works
A credit card gives you access to a revolving line of credit. You can use the card to make purchases, repay the amount you borrowed, and then use the available credit again.
Each month, the credit card issuer sends a statement. The statement usually includes your balance, minimum payment, payment due date, APR, fees, and other account information.
Many credit cards provide a grace period for purchases. If your card has a grace period and you pay the full statement balance by the due date, you can generally avoid paying interest on those purchases.
If you do not pay the full statement balance, interest may be charged on the amount you carry into the next billing cycle. Credit card companies often calculate interest using daily balances, which means interest can continue adding up while the balance remains unpaid.
For example, imagine carrying an unchanged $1,000 balance on a credit card with a 24% APR. Over approximately 30 days, the interest could be close to $20.
If you continue carrying the balance, more interest may be added. If you make new purchases, your balance may grow even faster.
The exact amount depends on the credit card agreement, daily balances, transaction dates, payments, fees, and billing cycle.
Statement Balance vs. Minimum Payment
The statement balance and the minimum payment are not the same thing. The statement balance is the full amount listed on your monthly statement. The minimum payment is the smallest amount you need to pay to keep the account from becoming past due. Paying only the minimum can help keep the account current, but it does not usually prevent interest. It can also cause the balance to take much longer to repay.
For example, imagine your statement balance is $500 and your minimum payment is $25.
Paying the full $500 by the due date may allow you to avoid purchase interest when a grace period applies.
Paying only $25 leaves $475 unpaid. Interest may be charged on the remaining balance, and the next statement may include that interest along with any new purchases.
Fixed and Variable Interest Rates
Some interest rates stay the same. Others can change. A fixed interest rate stays the same during the period described in the agreement. This can make payments easier to predict. Fixed rates are common on many auto loans, personal loans, certificates of deposit, and fixed-rate home loans. A variable interest rate may increase or decrease based on the terms of the account and changes to an outside rate or index. Variable rates are common on some credit cards, savings accounts, money market accounts, home equity lines of credit, and adjustable-rate mortgages. A variable savings rate may increase or decrease the amount you earn. A variable loan or credit card rate may increase or decrease the amount you pay. Before agreeing to a variable-rate product, review how often the rate can change and how those changes could affect your payment or earnings.
A Smaller Monthly Payment Can Cost More Over Time
A smaller monthly loan payment can look attractive, but it does not always mean the loan is cheaper.
A lender may lower the monthly payment by extending the loan across more months. This can make the payment easier to fit into a monthly budget, but it also gives interest more time to add up.
For example, a shorter-term auto loan may have a higher monthly payment but lower total interest. A longer-term loan may have a smaller monthly payment but cost more by the time it is completely repaid.
Before choosing a loan, look at both the monthly payment and the total amount you will repay.
The monthly payment tells you what needs to fit into your current budget. The total repayment amount shows you the bigger financial impact.
Ways to Pay Less Interest
Comparing several offers can help you find a lower borrowing cost. When reviewing similar loans, compare the APR, fees, term, monthly payment, and total amount you will repay.
A shorter loan term can also reduce the total interest, although the monthly payment will generally be higher. Choose a payment that fits comfortably into your budget and still leaves room for regular expenses and unexpected costs.
Making additional payments toward the principal may help reduce the balance faster. Before sending extra money, confirm how the lender applies additional payments and check for any early payoff penalties.
For credit cards, paying the full statement balance by the due date is one of the clearest ways to avoid purchase interest when a grace period applies.
Improving your credit can also help you qualify for more competitive rates in the future. Paying bills on time, managing credit card balances, and correcting errors on your credit reports can support your overall credit profile.
Refinancing may be another option if your credit improves or interest rates decrease. However, a lower monthly payment does not automatically mean refinancing will save money. Review the new fees, repayment term, and total cost before replacing an existing loan.
Questions to Ask Before Borrowing or Saving
Before taking out a loan, ask how much you are borrowing, what the APR is, how long the repayment term lasts, and how much you will repay in total. You should also review fees, fixed or variable rate terms, early payoff rules, and how additional principal payments are handled.
Before opening a savings account, ask about the APY, account fees, minimum balance requirements, withdrawal rules, and how easily you can access the money. For a certificate of deposit, review the term and early withdrawal penalty.
You do not need to memorize every financial formula. Understanding which numbers to look for and which questions to ask can help you make a more informed decision.
Need Help Looking at the Numbers?
Zing offers free financial coaching for members. A financial coach can help you review debt, understand credit, build a spending plan, or talk through a financial goal in plain language.
You can also explore Zing’s savings accounts, money market accounts, certificates of deposit, current rates, credit card options, and auto loans to learn more.
The examples in this article are for educational purposes and do not represent a current Zing rate, account offer, or loan approval. Rates, payments, fees, requirements, and earnings can vary.
*APR is Annual Percentage Rate. With approved credit and income verification. Rates are dependent on credit qualification, length of term, loan-to-value (LTV), age of vehicle, and if the vehicle is new or used. Rates are subject to change without notice.
**Hypothetical example for educational purposes only. This example assumes a $1,000 beginning balance, a constant 5.00% annual percentage yield (APY) for three years, all earnings remain in the account, and no additional deposits, withdrawals, or fees. It does not represent a current Zing Credit Union account, rate, APY, or guarantee of earnings. Actual earnings may vary based on the account’s terms, balance, account activity, fees, and changes in the APY. Rates for variable-rate accounts may change after the account is opened. Fees may reduce earnings. See Zing Credit Union’s current Rate and Fee Schedule and applicable account disclosures for current terms.
