Credit Card Payoff Calculator
Estimate how many months it takes to pay off a credit-card balance with a fixed monthly payment, given the card's APR. Uses the standard amortisation formula to translate "I can pay $X/month" into a concrete payoff timeline.
Last updated: May 2026
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About this calculator
The payoff time formula for a fixed monthly payment is n = ⌈-log(1 − (P · i) / M) / log(1 + i)⌉, where P is the current card balance, i is the monthly periodic rate (annual APR / 12 as a decimal), M is the fixed monthly payment, and n is the number of months until the balance reaches zero. This is the same amortisation math used for any fixed-payment loan, just applied to revolving credit-card debt as if it were a closed-end loan (which it can be if you stop using the card). Variables: cardBalance (P) is your current outstanding balance; interestRate is the card's APR; monthlyPayment is the fixed dollar amount you commit to paying each month. Critical edge case: M must exceed the monthly interest charge P · i for the balance to ever shrink. If M ≤ P · i, the argument inside the logarithm becomes ≤ 0 and the formula produces NaN — meaning your payment doesn't even cover interest and the balance grows over time (this is the trap of paying only the minimum, by design). The formula also assumes you stop making new charges on the card; every new purchase resets the math by adding to P and (because grace periods are lost once you carry a balance) immediately accruing interest. Real-world adjustments: most cards compound interest daily using the average daily balance method, so the actual payoff may differ slightly from this monthly-compounding formula (typically a few extra days). Promotional 0% APR balance transfers temporarily set i = 0; during that window every dollar of payment goes to principal, dramatically accelerating payoff if used aggressively.
How to use
Example 1 — Paying off in reasonable time. You owe $8,000 on a card at 19.99% APR and commit to $300/month. Enter Card Balance = 8000, Interest Rate = 19.99, Monthly Payment = 300. Monthly rate i = 0.1999/12 ≈ 0.01666. Monthly interest charge = 8000 · 0.01666 ≈ $133.27. Since $300 > $133.27, the balance will pay off. n = ⌈-log(1 − (8000 · 0.01666) / 300) / log(1.01666)⁾⁾⌉ ≈ ⌈-log(1 − 0.4441) / log(1.01666)⌉ ≈ ⌈-log(0.5559) / 0.01652⌉ ≈ ⌈35.6⌉ = 36 months. ✓ Three years to clear. Total paid: 36 × $300 = $10,800; interest cost ≈ $2,800. Example 2 — Increasing the payment dramatically. Same $8,000 at 19.99% APR but you commit to $500/month. Enter 8000, 19.99, 500. Monthly interest ≈ $133.27 < $500. n = ⌈-log(1 − (8000 · 0.01666) / 500) / log(1.01666)⌉ ≈ ⌈-log(1 − 0.2664) / 0.01652⌉ ≈ ⌈-log(0.7336) / 0.01652⌉ ≈ ⌈18.8⌉ = 19 months. ✓ Less than half the time and the total interest drops to ~$1,500 — saving roughly $1,300 by adding $200/month to the payment. The math heavily rewards aggressive payoff because every dollar above the interest charge attacks principal directly.
Frequently asked questions
How does the payoff formula work?
It's the standard fixed-payment amortisation formula rearranged to solve for time. The intuition: each month's interest charge equals current balance × monthly rate; your payment first covers that interest, and whatever's left reduces principal. The next month's balance is (balance − principal reduction). Repeating this until the balance hits zero gives a geometric-series sum, which solves to n = -log(1 − P·i/M) / log(1 + i). The ceiling function ⌈⌉ rounds up because partial months don't exist in payment schedules — you pay a final smaller installment in the last month. Same formula works for any loan with fixed payments: car loans, mortgages, personal loans. The only thing that makes credit cards different is that they're revolving (you can keep charging), and most use daily compounding rather than monthly — the daily-compounding adjustment typically affects payoff by less than 1%.
How can I pay off my card faster?
Three levers move the needle dramatically: (1) Increase the payment. Even small increases compound enormously — going from $200 to $300/month on a $5,000 balance at 22% APR cuts payoff from 39 months to 22 months and saves $1,400 in interest. (2) Lower the rate. Apply for a 0% balance-transfer card (typical 12–18 month no-interest window, ~3% transfer fee); pay off during the window and the interest savings can exceed the fee many times over. (3) Stop adding charges. Every new purchase loses grace-period protection once you carry a balance — it starts accruing interest immediately, undermining your payoff progress. Other tactics: pay twice a month rather than monthly (slightly reduces average daily balance), use windfalls (tax refunds, bonuses) for lump-sum principal payments, negotiate a hardship rate with your issuer (worth asking if you're struggling, especially with proof of financial difficulty).
Why does paying biweekly help more than paying monthly?
Two compounding effects. (1) Credit cards typically charge interest based on the average daily balance — making a payment mid-month rather than at month-end reduces the average daily balance for the second half of the cycle, saving a small amount of interest each month. (2) Paying biweekly (every 2 weeks) rather than twice a month (e.g., 1st and 15th) means you make 26 half-payments per year instead of 24 — equivalent to 13 monthly payments instead of 12, accelerating payoff by roughly one month per year. Over a 3-year payoff, the biweekly schedule clears the balance about 2–3 months faster and saves a few hundred dollars in interest. Not all card issuers report biweekly payments correctly, so check that your payments are credited promptly; the math only works if the issuer applies each half-payment as soon as it arrives.
What are the most common mistakes people make paying off credit cards?
The first is continuing to charge new purchases while paying down the balance — every new dollar borrowed at 22% offsets the interest savings from your payments, and new charges immediately accrue interest because the grace period is lost on cards with revolving balances. The second is paying only the minimum, which can take 20–30 years and cost 2–4× the original balance in interest. The third is closing paid-off cards without considering credit-score impact; closing reduces your total available credit, which raises your utilisation ratio and can drop your score 20–40 points (counter-intuitive, but real). The fourth is opening too many new cards for "rewards stacking" while carrying balances — the 1–3% cash back means nothing if you're paying 22% interest. The fifth is using home equity to pay off credit cards; you trade unsecured dischargeable debt for secured debt that puts your house at risk. Finally, people often forget that consistency matters — missed payments trigger late fees and potential penalty APR (often 29.99%), wiping out months of progress.
When should I not use this calculator?
Skip it when you plan to keep using the card during the payoff period; the formula assumes a fixed starting balance with no new charges, and ongoing spending invalidates the projection. Do not use it for cards in promotional 0% APR periods unless you adjust the rate to 0; during the promo, every dollar goes to principal, so payoff is just balance ÷ payment. It is the wrong tool for cards with deferred-interest promotions (common at electronics retailers); if you don't pay off in time, retroactive interest from day one applies to the full original balance — a much worse outcome than the formula suggests. Avoid it for multi-card payoff strategies (snowball or avalanche) where you need to iterate as each card is paid off; use a multi-debt planner. Finally, do not use it for accounts in collections or charge-off status; those typically have stopped accruing interest in the normal sense, and the relevant math is negotiating a lump-sum settlement, not amortising payments.