Credit Card Interest Calculator – Daily Interest, Payoff Time and Total Cost
This Credit Card Interest Calculator helps you understand how much your revolving balance really costs over time. Instead of guessing how interest, minimum payments and payoff plans work, you can see the numbers clearly: daily interest charges, minimum payment impact, payoff time, total interest cost, the effect of extra payments, and whether a balance transfer could save money.
Credit cards are flexible and convenient, but the combination of high APRs and minimum payments can keep balances around for years. A payment that looks comfortable today can lead to thousands in extra interest over time. This calculator is designed to show you where your money is going so you can build a repayment plan that fits your budget and reduces interest costs.
How the Credit Card Interest Calculator Works
The calculator is divided into seven modes that cover most of the questions people have about credit card interest:
- Daily Interest: Estimate daily periodic rate and interest for a specific number of days.
- Minimum Payment: See how much of your payment goes to interest versus principal in the first month.
- Payoff Time: Estimate months and years to pay off a card with a fixed monthly payment.
- Required Payment: Find the payment needed to pay off a balance in a chosen number of months.
- Total Cost of Debt: See total interest and total payments over the full payoff period.
- Extra Payments: Compare base payments versus extra payments and see time and interest savings.
- Balance Transfer: Estimate how an intro APR plus transfer fee compares to staying on your current card for the intro period.
Each mode uses standard formulas based on your APR and selected payment pattern. Results are estimates meant for planning, not exact billing calculations, since issuers may use slightly different methods and rounding rules.
Understanding APR and Daily Periodic Rate
APR (annual percentage rate) is the yearly interest rate on your credit card. Issuers generally convert APR into a daily periodic rate when calculating interest on your balance.
Daily Periodic Rate Formula
If your APR is 21.9%, your daily periodic rate is approximately 0.0219 ÷ 365 ≈ 0.00006, or 0.006% per day. The daily interest on a $3,000 balance would be Balance × Daily Rate.
Over a 30-day billing cycle, total interest is the sum of interest on your average daily balance. This calculator uses a simplified version by applying the daily rate to the balance for the selected number of days, which is a good approximation for many planning purposes.
Mode 1: Daily Interest Calculator
The Daily Interest tab lets you see how interest grows over time on a given balance and APR. You enter your current balance, APR, billing cycle length and number of days you expect to carry the balance.
Daily Interest for Selected Days
The calculator converts APR into a daily rate, multiplies it by your balance and then by the number of days. It also shows the effective interest rate for that period and the new balance after adding interest, assuming no payments.
Mode 2: Minimum Payment Impact
Minimum payments are typically calculated as a small percentage of your balance, sometimes with a fixed floor amount. While this keeps monthly payments low, it can greatly extend the time it takes to pay off the debt and increase total interest paid.
Minimum Payment and Principal Paid
If principal paid is small, your balance barely falls. If interest is higher than the minimum payment, your balance can even grow. The calculator shows how the first month’s minimum payment breaks down between interest and principal and what the new balance would be.
Mode 3: Payoff Time with a Fixed Monthly Payment
The Payoff Time mode answers the question: “If I pay a fixed amount every month, how long will it take to pay off this card?” It uses your balance, APR and chosen monthly payment to estimate the number of months to become debt-free.
Payoff Time Formula (Amortization)
Assuming a constant monthly payment greater than the monthly interest, the payoff time can be approximated using standard amortization formulas. The calculator then runs a month-by-month simulation to refine total interest and total amount paid.
You also see the payoff time expressed in years, which makes it easier to understand the long-term impact of too-small payments.
Mode 4: Required Monthly Payment to Pay Off in X Months
In the Required Payment mode, you flip the problem. Instead of asking “When will I be done?” you ask “What monthly payment do I need to be done in a certain number of months?”
Required Payment Formula
Here, r is the monthly interest rate (APR ÷ 12) expressed as a decimal, and N is the number of months. If the APR is zero, the calculator simply divides the balance by the number of months. The tool also sums total interest and total payments implied by that schedule.
Mode 5: Total Cost of Credit Card Debt
The Total Cost mode focuses on the big picture. Using your balance, APR and monthly payment, it estimates the payoff time, total interest and total amount paid over the life of the debt.
Total Interest and Payment Breakdown
The calculator also shows the percentage of total payments that go to interest instead of principal. Seeing that interest share can be a strong motivator to increase payments or adjust your payoff plan.
Mode 6: Effect of Extra Monthly Payments
Small extra payments can make a surprisingly large difference. The Extra Payments mode compares your base payment with a higher payment that includes an extra amount applied each month.
The calculator runs two payoff simulations:
- Base scenario: current balance, APR and base monthly payment.
- Extra scenario: same balance and APR, but with base payment plus extra payment each month.
From these two paths, it calculates how many months you save and how much interest you avoid paying by adding extra monthly payments. This helps you see whether an extra amount fits your budget and how powerful it can be over time.
Mode 7: Balance Transfer APR Comparison
Balance transfer offers often advertise a low or 0% introductory APR. However, they usually come with a transfer fee. The Balance Transfer mode compares interest on your current card with the cost on a new card, including the transfer fee, during the intro period.
Balance Transfer Cost Comparison
- Current card: monthly interest is applied at your standard APR; you make the same monthly payment for the intro period.
- New card: a transfer fee is added up front, and interest is charged at the intro APR for the same payment pattern.
The calculator sums the interest on the current card and the fee plus interest on the new card, then estimates savings over the intro period. This helps you judge whether a particular balance transfer is likely to reduce your costs, assuming you keep making payments and do not add new spending.
Why Understanding Credit Card Interest Matters
Credit card interest is a powerful force. Because interest accrues on a revolving balance, high APRs and long payoff times can make even moderate balances very expensive. Understanding how interest is calculated and how payments are applied helps you make more informed decisions, such as:
- Choosing a realistic and effective monthly payment amount.
- Avoiding over-reliance on minimum payments.
- Evaluating whether to consolidate or transfer balances.
- Seeing how extra payments accelerate debt freedom.
- Prioritizing which debts to pay off first.
Examples of Credit Card Interest Scenarios
Example 1: Daily Interest on a Balance
If you have a $2,500 balance at 19.99% APR, the daily periodic rate is roughly 0.01999 ÷ 365 ≈ 0.0000548. Daily interest is about $0.14. Over 30 days with no payments, interest would be about $4.11, adding that much to your balance.
Example 2: Minimum Payment Breakdown
Suppose you owe $3,000 at 21.99% APR and your minimum payment is 2% of the balance, with a $25 floor. Two percent of $3,000 is $60, so the minimum payment would be $60. Monthly interest is about $54.98, leaving just over $5 going toward principal. Your balance would barely move after one payment.
Example 3: Payoff Time with a Fixed Payment
On a $5,000 balance at 19.99% APR with a $200 monthly payment, the calculator estimates payoff in a few years, along with the total interest paid over that period. If you cut the payment in half, the payoff time and total interest rise sharply.
Example 4: Required Payment for a Two-Year Payoff
If your balance is $4,000 at 18.5% APR and you want to pay it off in 24 months, the Required Payment mode calculates the monthly payment you would need and the total interest cost for that plan.
Example 5: Extra Payment Savings
With a $7,000 balance at 19.99% APR, a $250 monthly payment might take many years to eliminate the debt. Adding an extra $100 per month can cut months off the payoff time and save a substantial amount in interest, which the calculator quantifies.
Example 6: Balance Transfer Comparison
Assume a $5,000 balance at 23.99% APR and an offer to transfer to a 0% intro APR for 12 months with a 3% fee. The calculator estimates the interest you would pay staying on the current card versus the fee plus any interest on the new card during the intro period, based on a chosen monthly payment.
How to Use This Tool Effectively
- Use the Daily Interest tab to see how fast interest accrues on your current balance.
- Check the Minimum Payment tab to understand how little progress minimum payments might make.
- Experiment with the Payoff Time and Required Payment tabs to build a realistic payoff plan.
- Review the Total Cost tab to understand how much interest a repayment plan will cost over time.
- Try different values in the Extra Payments tab to see how much faster you can become debt-free.
- Use the Balance Transfer tab to compare offers and avoid balance transfers that save little after fees.
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Credit Card Interest Calculator FAQs
Frequently Asked Questions About Credit Card Interest
Get quick answers about APR, daily interest, minimum payments, payoff time, extra payments and balance transfers.
Minimum payments are usually set low relative to your balance. A large portion of each payment goes to interest, leaving your principal almost unchanged. This keeps you in debt longer and increases the total interest you pay over time.
Most credit card issuers calculate interest daily using a daily periodic rate based on APR, then add the interest charge at the end of the billing cycle. If you pay your statement balance in full by the due date, many cards do not charge interest on purchases.
Paying a fixed amount that is higher than your minimum payment usually leads to faster payoff and lower interest than simply paying the recommended minimum percentage. The best approach is to pay as much as your budget comfortably allows.
There is no single answer. Use the Extra Payments tab to test different extra amounts and see how they change your payoff time and total interest. Choose a sustainable extra amount that fits your budget and financial goals.
Not always. Balance transfers may include fees, intro periods and higher rates after the intro expires. They can save money if you pay down the balance aggressively during the intro period. The Balance Transfer tab helps estimate if a specific offer is likely to reduce your costs, assuming disciplined payments and no new spending on the card.
No. Your statement is the official record of charges, interest and payments. This calculator is a planning tool that uses your inputs and typical formulas to show estimates for various what-if scenarios.