Build a debt payoff calculator that compares snowball and avalanche plans
People in debt want two answers: when will I be clear, and which debt should I attack first? A debt payoff calculator that lists each debt, applies a fixed monthly budget and compares payoff orders answers both. Anticode can build one that keeps the figures on the person's own device, which matters for something this private, and labels itself as a planning tool rather than advice.
Snowball, avalanche and the rest
Every method pays the minimum on every debt and puts any money left in the monthly budget towards one target debt. When that debt is cleared, its payment rolls on to the next target. The methods differ only in the order of targets.
| Method | Target order | Why people choose it |
|---|---|---|
| Avalanche | Highest interest rate first | Least interest paid overall, in arithmetic terms |
| Snowball | Smallest balance first | Quick early wins that keep people going |
| Custom | An order the user drags into place | A debt to a relative, or one with a penalty clause, may matter more than the rate |
| Minimums only | None | A baseline that shows the cost of doing nothing extra |
Showing all of them side by side, with total interest and payoff month for each, is more useful than telling users which is right. The gap is often smaller than expected, and the motivational case for snowball is real.
Inputs and the month-by-month engine
For each debt: a name, current balance, annual interest rate and minimum payment. Then one figure for the whole plan: the total the person can pay each month. The engine runs month by month: add a month's interest to each balance, pay minimums, send the remainder to the target, roll freed-up payments forward, and stop when everything is zero.
Edge cases decide whether the tool can be trusted:
- Budget below the sum of minimums. Say so immediately and stop; there's no plan to show.
- Minimum payment below a month's interest. That debt grows. Flag it in red rather than looping for ever.
- Promotional 0% periods. Ask for an optional end date after which the rate changes, common on balance-transfer cards.
- Last payments. The final month on each debt is smaller than the usual payment; the leftover should flow to the next target that same month.
- A cap on the run. Stop at, say, 50 years and report that the plan doesn't finish.
Screens that help someone stick to it
- Debts
- An editable list with balance, rate and minimum, sortable, with a total at the bottom.
- Plan
- The chosen method's payoff date, total interest and a chart of balances falling over time.
- Schedule
- A month-by-month table: what to pay on each debt this month. This is the screen people print and stick on the fridge.
- Progress
- Tick off each month's payments; update a balance when a statement arrives and the plan recalculates.
Everything is saved in the browser on the device, so the plan is there next month. Because a list of someone's debts is sensitive, the fact that nothing leaves the device is worth saying on the first screen. Pair it with the budget tracker or subscription tracker if you're building a wider money toolkit.
Writing the request
"A credit card payoff planner for a money-advice blog. Users add debts with balance, APR and minimum payment, set a monthly budget, and compare avalanche, snowball and a custom order. Show payoff date and total interest for each, a falling-balance chart and a printable monthly schedule. Warn when the budget doesn't cover the minimums. Save on the device. Label it a planning tool, not financial advice. Calm, plain, high-contrast design."
Before publishing, test it against a statement you know: the first month's interest should match the card's figure to within rounding. Card issuers calculate interest on daily balances, so a monthly model will drift slightly, which is another reason for the planning-tool label.
What it doesn't do
- No bank connections. It can't read balances from a bank or card account; figures are typed in.
- No advice. It doesn't know about income, other commitments, insolvency options or debts with legal consequences. Link to a free debt-advice service relevant to your readers' country.
- No sync or backup. The plan lives in one browser. Ask for an export file if users want a copy.
- No reminders. It can't notify anyone when a payment is due.
Questions people ask
Is the debt snowball calculator result different from avalanche every time?
Only when the smallest debt isn't also the highest-rate one. If they line up, both methods produce the same plan.
Can it handle loans with fixed payments, like a car loan?
Yes. Treat the fixed payment as the minimum. Any extra the budget sends there shortens the loan, if the lender allows overpayments.
Does anyone else see the numbers I enter?
No. The calculator runs in your browser and saves to that device. Nothing is sent to the site owner or to Anticode.