Credit Card Interest Calculator Instantly

Key Features and Benefits

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  Payoff Timeline Projection — Enter your balance and your planned monthly payment, and the calculator shows you exactly when you will be debt-free. A 3-million-won balance at 20 percent APR with minimum payments of 90,000 won per month takes about 44 months to pay off — nearly four years. Increase that payment to 150,000 won and the payoff drops to 23 months. Seeing the timeline in months rather than vague years makes the impact of payment size tangible.
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  Minimum Payment Trap Analysis — The calculator highlights the cost of paying only the minimum. Most Korean credit cards set the minimum at 10 percent of the outstanding balance or a fixed floor amount — whichever is greater. Paying the minimum on a 5-million-won balance at 18 percent APR means you will pay approximately 2.4 million won in interest before the balance reaches zero. That is nearly half the original balance paid purely in interest. The analysis shows this cost explicitly so you can decide whether the minimum is truly the most you can afford.
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  Daily Periodic Rate Breakdown — See your APR converted to the daily periodic rate and watch how daily interest accumulates over a billing cycle. This granular view explains why your balance seems to shrink so slowly despite regular payments. Understanding that interest is calculated daily — not monthly — changes how you think about the timing of payments. Making a payment on the 1st of the month rather than the 15th reduces the average daily balance and therefore reduces the interest charged for that cycle.
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  Balance Transfer Comparison — Model the savings from transferring your balance to a lower-rate card. Enter the new card APR, the balance transfer fee (typically 2 to 3 percent of the transferred amount), and the promotional period length. The calculator compares the total cost of keeping the balance on your current card against the cost of transferring it. A transfer makes sense only when the interest savings exceed the transfer fee — and the calculator does that math for you.
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  Debt Payoff Strategy Simulator — If you carry balances on multiple cards, the calculator models two popular repayment strategies. The avalanche method directs extra payments to the highest-rate card first — this minimizes total interest paid. The snowball method targets the smallest balance first — this generates psychological wins that keep you motivated. Enter all your card balances and rates, set your total monthly payment budget, and compare the total interest cost under each strategy.
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  Grace Period Explanation — The calculator clarifies when interest starts accruing. If you pay your statement balance in full by the due date each month, most Korean credit cards do not charge interest — this is the grace period, typically 15 to 50 days depending on the issuer and billing cycle. The moment you carry any balance past the due date, you lose the grace period on new purchases too. The calculator models this so you can see the cost difference between full payment and partial payment habits.

How to Calculate Your Credit Card Interest

1. 1

   Find Your Current Balance

   Check your most recent credit card statement or log into your card issuer's app. You need the outstanding balance — the amount that carried over from the previous billing cycle plus any new charges minus any payments. If you have multiple cards, note the balance for each one separately. In Korea, you can also check your total credit card debt through the Korea Credit Information Services (한국신용정보원) portal. Use the exact figure from your statement, not a rounded estimate, because interest calculations are sensitive to the starting balance.

2. 2

   Enter Your APR

   Your card's APR is listed on your monthly statement and in your card agreement. Korean credit cards may have different APRs for different transaction types — purchases, cash advances, and revolving credit often carry different rates. Cash advances typically have the highest rate, sometimes exceeding 20 percent, and they begin accruing interest immediately with no grace period. Enter the rate that applies to the type of balance you are carrying. If you are unsure, use the revolving credit rate, as that is what applies to unpaid statement balances.

3. 3

   Set Your Monthly Payment Amount

   Decide how much you will pay each month. The minimum payment is the floor — paying less triggers late fees and damages your credit score. But paying the minimum is the slowest and most expensive path to becoming debt-free. A useful exercise is to enter three amounts: the minimum, double the minimum, and the maximum you can realistically afford. Compare the payoff timelines and total interest costs for each. The difference between minimum and double-minimum payments is often startling — doubling your payment can cut your payoff time by more than half and save you 40 to 60 percent in total interest.

4. 4

   Review the Interest Accumulation

   The calculator breaks down each month showing how much of your payment goes to interest and how much reduces the principal. In the early months of repayment on a high-APR card, interest can consume 50 to 80 percent of your payment. As the balance decreases, more of each payment goes to principal and the process accelerates. This is why the last few months of payoff feel faster than the first few — the math is literally working harder in your favor as the balance shrinks. Understanding this curve helps you stay patient during the slow early phase.

5. 5

   Model a Balance Transfer If Applicable

   If your card charges more than 15 percent APR and you qualify for a balance transfer offer at a lower rate, enter the transfer details. Typical Korean balance transfer promotions offer rates between 3 and 9 percent for 6 to 12 months, with a one-time transfer fee of 1 to 3 percent. The calculator compares the total cost of staying on your current card versus transferring. Key caveat — if you do not pay off the transferred balance within the promotional period, the rate reverts to the standard APR, which may be even higher than your current card. The calculator models this reversion so you can plan your payments to clear the balance before the promotional rate expires.

6. 6

   Compare Avalanche and Snowball Strategies

   If you have balances on multiple cards, enter each balance and APR into the multi-debt comparison feature. Set your total monthly payment budget — the sum you can allocate across all cards. The avalanche method ranks your debts by interest rate and attacks the highest-rate balance first while making minimum payments on the rest. The snowball method ranks by balance size and attacks the smallest balance first. Mathematically, avalanche always wins — it minimizes total interest. Psychologically, snowball often wins because eliminating a card balance entirely provides a motivational boost. The calculator shows the total interest cost for each method so you can make an informed choice based on your personality and circumstances.

Expert Tips for Managing Credit Card Debt

Related Tools

Credit card interest is the most expensive form of consumer debt most people carry, and managing it well means understanding how it connects to your broader financial obligations. The Loan Interest Calculator helps you evaluate whether converting credit card debt to a lower-rate installment loan saves you money after accounting for fees and terms. The Mortgage Calculator shows how your credit card balances factor into DSR calculations when you apply for a home loan — high revolving debt can reduce the amount you are approved to borrow. And the Salary After Tax Calculator reveals exactly how much cash you have available each month after mandatory deductions, giving you a realistic number for your debt repayment budget. Tackling credit card debt is easier when you see how every piece of your financial life fits together.