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Debt Payoff by Extra Payment Calculator
Model your balance and rate, compare extra-payment scenarios, and reverse-solve the amount a target debt-free date needs.
Open the debt payoff by extra payment calculatorThe three strategies
- Avalanche: pay minimums on everything, and send every spare dollar to the highest interest rate. Mathematically optimal — it always produces the lowest total interest and the earliest overall debt-free date.
- Snowball: pay minimums on everything, and send every spare dollar to the smallest balance. Costs more interest, but closes accounts sooner, which some people find far easier to keep up.
- Flat extra payment: no reordering at all — just add a fixed amount to one loan every month. Simplest to automate, and the right choice when you only have one meaningful balance.
How big is the gap in practice?
The avalanche advantage grows with the spread between your interest rates. If one balance is at 24% and another at 5%, ordering matters a great deal. If everything sits between 6% and 8%, the difference between avalanche and snowball on typical consumer balances is often small — a few hundred dollars and a month or two — while the amount you pay extra is worth thousands.
| Situation | Usually the better fit | Why |
|---|---|---|
| Wide rate spread (a card at 20%+ alongside a low-rate loan) | Avalanche | The interest saving is large and obvious |
| Several small balances, similar rates | Snowball | Closed accounts arrive quickly and keep momentum |
| One main balance | Flat extra payment | There is nothing to order; size the extra amount instead |
| Motivation has failed before | Snowball | The strategy you keep beats the one you abandon |
Size beats ordering
On a $20,000 loan at 7% over 60 months, going from no extra payment to $100 a month saves roughly $890 in interest and 13 months. No amount of reordering delivers that on a single balance. Decide the amount first, then decide the order — and see how much extra to pay each month for how the returns taper.
Setting it up so it survives
- 1List every balance with its rate and minimum payment. The rate is what decides ordering under avalanche.
- 2Fix the total amount you will put toward debt each month, and hold it steady as balances close — that is the mechanism that makes both avalanche and snowball accelerate.
- 3Automate it, and confirm extra amounts are applied to principal rather than held as a future payment.
- 4Keep a small buffer. Falling back onto a card at 24% undoes months of progress.
- 5Run revolving balances separately with the credit card payoff calculator, and model fixed loans with the extra-payment payoff calculator.
These are arithmetic comparisons, not financial advice. Consider your own circumstances, and get professional help if debt payments are not currently affordable.
Frequently asked questions
- Does consolidation change the picture?
- It can lower the blended rate and simplify the payment, which helps if the new rate is genuinely lower after fees. It does not reduce the balance, and extending the term can raise total interest even at a lower rate.
- Should I stop retirement contributions to clear debt faster?
- Giving up an employer match is an immediate cost that is hard to beat. High-rate debt is a strong argument for redirecting money above the match; below it, the trade is much less clear. This depends on your situation.
- What about balance-transfer offers?
- A 0% promotional period can save real interest if you clear the balance before it expires and account for the transfer fee. Work out the payment needed to finish inside the promotional window before committing.
Assumptions and limits
Every figure on this page comes from the assumptions stated beside it, calculated with the same formulas the linked tools use. Rates, taxes, insurance and running costs vary by lender, state and household, so substitute your own numbers before acting. Nothing here is a lending decision, a tax opinion, or financial advice.
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