Calculate how long it takes to pay off credit card debt. Includes interest saved, payoff date, and month-by-month amortization schedule.
Monthly payment to clear in N months: PMT = Balance × (r / (1 − (1+r)^−N))
where r = monthly rate = APR ÷ 12 ÷ 100.
Months to clear at fixed payment: N = −log(1 − (Balance × r / PMT)) ÷ log(1 + r)
Total interest = (PMT × N) − Balance
Worked example: 3,000 balance at 24% APR (r = 2%/month), 100/month payment. N = −log(1 − (3000 × 0.02 / 100)) ÷ log(1.02) = 42 months (3.5 years). Total paid = 4,200. Total interest = 1,200 (40% of original balance). Increasing monthly payment to 150 clears the same balance in 24 months with only 600 in interest.