Credit cards can feel like extra spending power, but they are borrowed money that must be repaid. Credit cards can lead to costly debt if you carry a balance or miss payments. That debt comes from credit card interest.
We'll explain what credit card interest is, how it's calculated, when it can be charged, and practical ways to reduce or avoid it.
What credit card interest is
Credit card interest is the fee charged when you borrow money from your credit card issuer and don't pay it back in full by the due date. When you buy something with your card, the issuer pays the merchant on your behalf. If you don't pay the full balance by your due date, they charge you a percentage of what you owe.
When credit card interest gets charged
You don't get charged interest the second you tap your card. Credit cards come with a billing cycle (usually about 30 days) and a grace period (usually 21 to 25 days after your statement is issued). If you pay your full statement balance before the grace period ends, you pay zero interest.
But if you carry a balance past the due date, charges begin. Once you lose the grace period, new purchases can also accrue interest daily, which can make balances harder to pay down.
Why it's important to understand credit card interest
The details of credit card interest rates may seem like fine print you can ignore, but understanding how they work helps you save money and keep more of what you earn.
When you know how credit card interest works, you're in a better position to avoid additional fees, steer clear of (or at least minimize) debt, and maintain a solid credit score.
APR vs interest rate
You'll often see the term annual percentage rate (APR) on your credit card statement. For credit cards, the APR is typically the same as the interest rate shown on the statement — it represents the yearly cost of borrowing. Because interest is calculated daily, that annual rate is divided by 365 to get your daily rate.
Types of credit card interest
Not all credit card transactions are treated equally. Most credit cards charge three different interest rates:
Purchase rate: applies to everyday purchases such as groceries and gas (typically 19.99% to 20.99%).
Cash advance rate: applies when you withdraw cash or make cash-like transactions; it is usually higher than the purchase rate and typically has no grace period, so interest starts immediately.
Penalty rate: applies if you miss a minimum payment or exceed your credit limit, and it is usually much higher than the purchase rate.
How credit card interest is calculated
Interest on purchases is what you'll be dealing with most of the time. It's listed as the APR on your statement, accrued daily, and charged monthly. The interest compounds, meaning each day's interest gets added to your balance, and the next day's interest is calculated on that slightly higher amount.
Here's how the math works:
Convert APR to a daily rate (daily periodic rate): 20.99% ÷ 365 = 0.0575% per day.
Calculate daily interest: $948 × 0.0575% = $0.55 on day one (slightly more each day after due to compounding).
Monthly interest charges: after 30 days, you would be charged $16.57 in interest, bringing the balance to $964.57.
Remember: you generally only pay interest if you don't pay your full statement balance by the due date. If you pay in full within the grace period (often 21 to 25 days), you typically pay no interest on purchases.
Key distinction: "full statement balance" matters. Here's why:
Pay in full: No interest charges, grace period continues
Pay the minimum: Interest kicks in on the remaining balance and compounds monthly
Pay nothing or late: Interest charges plus potential penalty rates
How credit card interest works in Canada
In Canada, federal regulations require credit card issuers to be transparent about interest charges. By law, Canadian credit cards must offer a minimum 21-day grace period on new purchases. Your statement must clearly show your interest rates, how long it will take to pay off your balance with minimum payments, and the total interest you'll pay.
How to avoid credit card interest charges
One advantage of credit card interest is that you can often avoid it by doing the following:
Pay your balance in full. Pay the full statement balance by the due date, not just the minimum payment.
Avoid cash advances. They often have no grace period and may carry higher rates and fees, so consider other options first.
Consider a lower-rate card. If you expect to carry a balance, a lower APR can reduce interest charges.
Use a budget. A simple framework like the 50-30-20 rule helps you spend within what you can pay off, avoiding carried balances and interest charges.
