Credit Card Interest Calculator

The CardRatings credit card interest calculator estimates your costs using a daily periodic rate. It assumes a consistent APR and balance throughout the billing cycle, though actual charges may vary based on additional purchases or payments. Enter your balance, APR and billing cycle length to see your estimated monthly interest, projected statement balance, daily interest charge, and the total amount owed if your balance remains unchanged for 12 months. 

Step-by-step instructions

There are four bits of information that are necessary to see how much interest you’d pay based on your monthly payment, or in a specific period:

Step 1: Enter your current balance on your credit card. Find the total amount of your current balance on your credit card statement and enter that amount in the first field. Do not include a dollar sign or commas in your entry, but you can include a decimal.

Step 2: Enter the current interest rate charged by your credit card. Your interest rate may be expressed on your statement as APR, or annual percentage rate. This may have changed since you first signed up for the card, so check your latest statement for the current rate. Enter the percentage interest rate without adding a percent sign.

Step 3: Enter the number of days in your billing cycle.

Step 4: Click “Calculate interest.” The results panel returns four numbers: your estimated interest for the billing cycle, your projected statement balance, your daily interest, and the total you’d pay over 12 months if the balance stays where it is.

Try our quick start presets

Three preset scenarios load realistic values so you can see how interest scales with different balances and rates:

• Starter debt – A smaller balance at an average APR, closer to what someone who recently started carrying a balance might see.
• Typical revolving – A balance close to the U.S. average at a rate near the current national average, showing what most cardholders actually pay each month.
• High-pressure month — A larger balance at a high APR, showing how quickly interest compounds when both are elevated. 

Each preset is a starting point. Adjust the balance, APR, or billing cycle to match your own situation. 

How does credit card interest work?

Credit card interest is the cost you pay for borrowing money when you carry a balance on your card from one billing cycle to the next. It’s usually expressed as an annual percentage rate (APR). If you don’t pay your full statement balance by the due date, interest accrues daily on the outstanding balance. This daily interest is calculated by dividing your APR by 365 and multiplying that daily rate by your average daily balance. The longer you carry a balance, the more interest you’ll accumulate. Paying your balance in full each month is the best way to avoid paying credit card interest.

For example: Say you carry a $2,000 balance on a card with a 22% APR and a 30-day billing cycle. Your daily interest rate is 22% ÷ 365, or 0.0603%. With daily compounding, that $2,000 balance grows to roughly $2,036.68 by the end of the cycle, so you’d owe about $36.68 in interest for the month. Leave that same $2,000 balance untouched for a full year and you’d pay around $490 in interest, nearly a quarter of what you originally owed.

How to calculate credit card interest

Banks use one of two methods to calculate interest: the daily periodic rate or the monthly periodic rate. The CardRatings calculator uses the daily periodic rate with daily compounding, matching what most major U.S. issuers do. Your cardholder agreement or statement will confirm which method your bank uses.

How to calculate interest based on a daily periodic rate method

1. Locate your balance, current APR, and number of days in your billing cycle on your credit card statement. Let’s stick with a balance of $1,000 and an APR of 16.99%. Let’s say your billing cycle was 30 days.
2. Divide your APR by 365 (for the 365 days of the year): 16.99% / 365 = about .0465% for your daily APR
3. Multiply your daily APR (.0465%) by your balance ($1,000) to find your daily periodic rate. In this case, $1,000 x .000465 (we moved that decimal point because it’s a percentage) = $0.47 for your daily periodic rate.
4. To find the interest due, multiply your daily periodic rate by the number of days in your billing cycle; therefore, 30 days x $0.47 = $14.10 in interest.
5. Keep in mind: With the daily periodic rate, your balance will increase each day by the amount of interest charged for the previous day – it’s called compounding interest. For instance, based on our example above, if your balance was $1,000 on day one, it will be $1,000.47 on day two and so on. This calculator takes this into account. 

How to calculate interest based on a monthly periodic rate method

1. Locate your balance and current APR on your credit card statement. For example, let’s say your balance is $1,000 and your APR is 16.99%
2. Divide your APR by 12 (for the 12 months of the year): 16.99% / 12 = about 1.42%
3. Multiply that number by your current balance. Remember, to multiply percentages, you have to move the decimal two places to the left. For this example, that means multiply $1,000 (your balance) by .0142 to get $14.20 interest for that month

The methods above are intended to give you a general idea of the process. They assume you aren’t making payments or additional purchases throughout the billing cycle. Credit card issuers could use a daily average balance calculation, which means they average your balance out over your billing cycle to find your interest due. Or, they could use a daily balance method that individually considers your balance on each day of your cycle to find the amount of interest due, in which case, making a payment toward your balance at the beginning of a billing cycle could actually save your money.

What is a credit card grace period?

A credit card grace period is the window between the end of your billing cycle and your payment due date, usually around 21 days. If you pay your full statement balance by the due date, no interest is charged on new purchases from that cycle.

• A partial payment ends the grace period. If you pay less than the full statement balance, interest starts accruing on your remaining balance immediately. New purchases in the next cycle also start accruing interest from the transaction date.
• Grace periods don’t apply to cash advances or balance transfers. Interest on those usually starts the day the transaction posts.

If you pay your balance in full every month before the grace period ends, your purchase APR is irrelevant because you will not be charged interest on those purchases.

How is cash advance interest different?

A cash advance is when you use your credit card to withdraw cash from an ATM, buy a money order, or complete a similar cash-equivalent transaction. Issuers treat these very differently from regular purchases:

• No grace period. Interest starts accruing the moment the transaction posts. There’s no “pay in full” option to avoid it.
• Higher APR. Most cards charge a separate cash advance APR, typically 5% to 10% above the purchase APR.
• Upfront fee. Expect a cash advance fee of about 3% to 5% of the amount withdrawn, with a minimum of $5 to $10.

To estimate cash advance interest, use your card’s cash advance APR in the calculator above, not the standard purchase APR. Interest starts the day the transaction posts, so count the days from that date rather than a full billing cycle. 

What is variable APR?

A variable APR is an interest rate on a credit card that fluctuates over time rather than remaining fixed. When the underlying benchmark rate changes, your card’s APR automatically adjusts by the same amount.

How Variable APR Works

• The formula: Issuers calculate your rate as Prime Rate + Margin.
  • Your variable APR = U.S. Prime Rate + issuer margin
• The Prime Rate driver: The U.S. Prime Rate tracks the Federal Reserve’s federal funds rate. When the Fed cuts or raises interest rates, your variable APR goes up or down accordingly — no advance notice required.
• Credit-based margins: Your specific margin is determined when you apply, based on your credit score. It typically looks something like:
  • Excellent credit: Prime Rate + 10% (lower APR)
  • Good/fair credit: Prime Rate + 20% (higher APR)

In both cases, if the Prime Rate increases by 0.25%, both cardholders’ variable APRs immediately increase by 0.25%. 

Does variable APR affect you?

• If you pay in full every month: The APR — variable or fixed — has zero financial impact on your purchases because you remain within the interest-free grace period.
• If you carry a monthly balance: Any rate increase directly raises your daily interest charges and overall monthly debt cost.

 ➤  LEARN MORE: How does the Federal Reserve impact credit card interest?

How can you lower your credit card interest rate?

The better your credit score, the more likely you’ll earn a favorable interest rate. That said, one of the best ways you can lower your credit card interest rate is to maintain a good credit score. You can do this by paying your balance on time, carrying a low balance, and keeping a low credit utilization ratio.

You can also take advantage of promotional APR offers. If you need to make a large purchase and need extra time to pay it off, consider a 0% intro APR credit card which offers an interest-free promotional period on purchases before regular APR applies. Alternatively, you could take advantage of a balance transfer offer which would allow you to transfer a high-interest debt to a card offering 0% intro APR, thus giving you time to pay off your balance interest-free.

Finally, you can ask your credit card issuer to lower your rate. It isn’t guaranteed, but issuers regularly reduce rates for cardholders who ask, especially those with a strong payment history. Come to the call with your current APR, balance, and length of time as a cardholder in front of you. Reference competing offers if you’ve received any at a lower rate. Ask for a specific reduction, like two percentage points, rather than a general “lower rate.” If the first agent says no, politely ask to speak with a retention specialist.

How do you avoid interest charges on a credit card?

As we mentioned above, the best way to avoid paying credit card interest is to avoid carrying a balance altogether, but again, we get this isn’t always possible.

If you can’t pay off your balance in full, do be sure to try and pay it down as much as you can, and if that’s still not feasible, consider transferring your balance to a balance transfer credit card with a 0% intro APR period to give yourself some more time.

When you’re comparing 0% intro APR offers, three variables determine whether the transfer saves you money. The intro period length matters most as the best balance transfer cards offer 0% intro APR periods up to 21 months, and a longer window means more of your balance can be paid down before the regular APR kicks in. The balance transfer fee comes next; most cards charge 3% to 5% on the transferred amount, so a $5,000 transfer costs $150 to $250 upfront. That fee is usually still worth paying if the intro period is long enough. Finally, check the regular ongoing APR that applies once the intro period ends, since any balance still on the card at that point starts accruing interest at the standard rate.

Compare our full list of balance transfer credit cards to see current 0% intro APR offers and terms. 

Quick reference: Monthly interest at common APRs 

Estimated monthly interest charges on common balances at common APRs, using daily compounding over a 30-day billing cycle:

Figures assume a constant balance and a 30-day billing cycle. Your actual monthly interest may vary if you make purchases or payments during the cycle. Use the calculator above for a custom estimate.