A credit card payoff calculator turns three numbers — balance, APR and monthly payment — into the two that actually matter: how long until the card is clear and how much interest you'll pay getting there. It works by reducing-balance math: each month interest is added at balance × (APR ÷ 12), your payment comes off, and the cycle repeats. The big lesson it teaches is that small increases in the monthly payment cut the total cost out of all proportion — because every extra dollar attacks the principal directly.
Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: standard amortization math, recomputed in code. Not financial advice.
How the payoff math works
Here r is the monthly rate (APR ÷ 12 ÷ 100), B the balance and P the payment. The closed-form gives the month count directly; the calculator above runs the month-by-month loop so it can also total the interest and find your payoff date. One hard rule: the payment must exceed the first month's interest (B × r) or the balance never falls.
Worked example — $5,000 at 18% APR, $200/month
Scenario: balance $5,000, APR 18% (so r = 0.18 ÷ 12 = 0.015), paying $200 each month.
Thirty-two months — about 2 years 8 months — and roughly $1,314 of interest. Now watch what paying more does on the same card: bump the payment to $300 and it's gone in 20 months for $797 of interest; pay $500 and it's 11 months and just $458. Drop to $100 and it stretches to 94 months with $4,311 of interest — nearly the original balance again. That spread is the whole reason minimum payments are so costly.
Frequently Asked Questions
$5,000 at 18% APR: $200/mo → 32 months, $300/mo → 20, $500/mo → 11. Paying more shortens it fast.
$5,000 @ 18%: ~$1,314 at $200/mo, $4,311 at $100/mo, just $458 at $500/mo.
Most of a minimum payment is interest. At $5,000/18%, month-one interest is $75 — pay near that and you barely move.
Yes — extra goes straight to principal. Highest-APR-first (avalanche) saves the most interest.
No — fixed APR and payment, no new charges or fees. Stop spending on the card to clear it fastest.