Enter your current balance, the annual interest rate (APR), and what you pay each month. The calculator runs the actual amortization schedule and shows the number of payment months until zero, the honest final partial payment, the total you will hand over (the sum of real payments), and the interest cost — and it warns you when a payment is too small to ever finish the job.
Method: the real repayment schedule
Each month the balance grows by its interest (balance × APR/1200) and then your payment lands. The calculator repeats exactly that until what remains (with its interest) fits inside one payment — that last month you pay only the remainder, so months is a whole number of payments and total paid is the sum of the payments actually scheduled, never payment × a fractional formula-month. At 0% APR the schedule is straight division with an honest final remainder.
Worked examples (schedule-exact)
- 10,000 at 18% APR paying 300/month → 47 payment months (46 × 300 + final 167.21), total 13,967.21, interest 3,967.21.
- Same debt paying 450/month → 28 payment months (27 × 450 + final 105.56), total 12,255.56, interest 2,255.56 — about 43% less interest and 19 fewer months than at 300.
Limits
The model assumes a fixed APR, a fixed monthly payment, and no new charges on the account — real credit cards add purchases, change rates, and charge fees, all of which lengthen the true payoff. Treat the result as the disciplined-case floor, and see the linked guide for strategies when juggling several debts.