Method
Total payment = monthly payment + extra payment. Each month interest of (annual rate / 100 / 12) x balance is added and the total payment is subtracted, until the balance reaches zero.
If the total payment is not larger than the first month of interest, the balance never falls and the payoff time shows 1200+ months.
Worked example
| Total debt | $24,000 |
|---|---|
| Annual rate | 18% |
| Monthly payment | $700 |
| Extra payment | $100 |
| Payoff time | 3y 5m |
| Estimated interest | $8,124 |
| Monthly payoff | $800 |
Assumptions and limits
- Your debts are modelled as one combined balance at one average rate. The calculator does not order several debts from smallest to largest, so it estimates the payoff time rather than a full snowball schedule.
- Fees, rate changes and new borrowing are not modelled.
Educational estimate only. It is not financial, tax, legal, or investment advice.