- If your payment is below the monthly interest charge, the balance never shrinks — the calculator flags this.
- Extra payments reduce the balance interest is calculated on every following month, so savings compound.
- The avalanche method (highest rate first) minimizes total interest; the snowball method (smallest balance first) maximizes early momentum.
- This uses the same payoff math as Hunch's in-app debt tracking.
How the debt payoff calculator works
Enter your current balance, interest rate, and monthly payment. The calculator simulates the balance forward month by month — charging interest, then applying your payment to the remainder — until the balance hits zero, showing the payoff date and total interest paid.
The math: amortizing a revolving or installment balance
Each month, interest accrues on the current balance (annual rate ÷ 12, applied to the balance), and your payment is applied after that interest charge — first covering the interest, with anything left over reducing principal. Because the balance shrinks a little each month, the interest charge shrinks too, which is why fixed payments pay off debt at an accelerating pace over time.
Worked example
A $8,000 credit card balance at 21.99% APR with a $300/month payment takes about 32 months to pay off, with roughly $1,650 in total interest. Bump the payment to $400/month and it drops to about 22 months and roughly $1,070 in interest — 10 months and $580 saved from one extra payment size.
Key terms
- APR
- Annual Percentage Rate — the yearly cost of borrowing, including interest (and sometimes fees), expressed as a percentage.
- Avalanche method
- Paying minimums on all debts but directing extra payments to the highest-interest-rate debt first — minimizes total interest paid.
- Snowball method
- Paying minimums on all debts but directing extra payments to the smallest balance first — builds psychological momentum from quick wins.
- Minimum payment
- The smallest payment a lender requires each month — often barely covering interest on revolving debt like credit cards.