Debt avalanche calculator

The calculator simulates one month at a time and stops when every balance is zero. Each month, every open debt is charged interest = round(balance × APR ÷ 12), rounded to the smallest unit of your currency and added to its balance. Every minimum is then paid, capped at the balance so a final payment can never overpay. Whatever is left of the budget goes to the current avalanche target, and if that target is cleared with money to spare, the remainder cascades to the next debt in the same month.

The avalanche order is fixed at the start: debts are sorted by APR from highest to lowest. Ties go to the smaller balance, then the larger minimum, so the result is the same however you typed the rows. Because the total budget never changes, the minimum of a cleared debt automatically joins the payment on the next one; the roll-over that the snowball is named for applies to the avalanche just the same.

If you enter the budget as an extra amount, the calculator adds up the minimums you typed and uses budget = Σ minimums + extra. The comparison strip runs the snowball order (smallest balance first) through exactly the same simulation, and the chart’s second line runs the same simulation with the budget set to the sum of today’s minimums and nothing more. Total interest is the sum of every month’s interest charges; total paid always equals the starting balances plus that interest. The full rules, rounding and tests are on the methodology page.

Full method, rounding and tests on the methodology page

The avalanche is the arithmetic answer. Every unit of budget sent to the highest-rate debt stops more interest than the same unit sent anywhere else, so with a fixed budget and fixed rates no other order costs less. In the worked example that is 275.50 over 18 months. With three debts of 8,000 at 27%, 2,500 at 19% and 900 at 9% and a budget of 600, the avalanche clears the 8,000 in month 21, the 900 in month 22 and the 2,500 in month 24, for 2,943.53 of interest; the snowball takes 25 months and 3,426.90, so the avalanche saves 483.37 and a month in that scenario.

The trade-off is patience. The highest-rate debt is often also a large one, so the first cleared account can be a long way off: month 16 in the example, against month 5 for the snowball, and month 21 in the three-debt case against month 3. Some people find a plan with no visible wins for a year hard to stick to, and a plan abandoned halfway costs more than either order followed to the end. Whether that matters is personal; the calculator’s job is to show both numbers.

How much the avalanche saves depends on the spread of your rates. Two debts at nearly the same APR leave little for the avalanche to exploit, and if the highest-rate debt is also the smallest, both orders start in the same place and the difference can be zero. The debt payoff calculator puts both orders side by side with the same inputs, and the guide to how credit card interest works explains why a high APR compounds so quickly on a card.

The payoff order table lists your debts in avalanche order with the start balance, the minimum, the month (or date, if you entered a start month) it is cleared and the interest it collected along the way. The highest-rate debt is at the top and usually accounts for most of the interest, so its row shows where the avalanche is doing its work. The comparison strip gives the snowball’s months and interest on the same inputs and states the difference in plain words.

The balance chart plots the total owed at the end of each month under the avalanche against a second line labelled “today’s minimums, fixed”. That line keeps paying the sum of the minimums you entered every month and nothing more. In the example that is 200 a month, which takes 65 months and 5,315.88 of interest; the avalanche at 500 a month takes 18 months and 1,146.87. The line is a fixed-payment comparison, not a model of a card issuer’s declining minimum; the credit card minimum payment calculator models that for a single card.

Two warnings can appear. If your total budget is below the sum of the minimums, the calculator names the shortfall instead of producing a plan. If a debt’s minimum is less than its first month’s interest, it is flagged as never repaid at the minimum. Under the avalanche such a debt is usually near the front of the queue, because a minimum that fails to cover interest is a sign of a high rate, so it is normally dealt with early.

Your numbers stay in your browser. DebtWren works out your results on your device. We don’t send the balances, rates or payments you type to our servers or store them. If you allow analytics, we record only broad ranges (for example “£2,000–£5,000 of debt”) to understand how the calculators are used. Like any website with ads, this page also loads advertising scripts; see our Privacy Policy.

The calculator is plain code running in this tab. It makes no network requests with your figures, and nothing is saved when you leave unless you choose to keep it. Read the privacy policy for how ads and analytics work on this site.

• Consumer Financial Protection Bureau — How to reduce your debt (highest rate first and smallest balance first)
• Consumer Financial Protection Bureau — What is a credit card interest rate? What does APR mean?
• Consumer Financial Protection Bureau — The minimum-payment box on a credit card statement
• Federal Reserve — Consumer Credit (G.19) statistical release

Estimates for general information only — not financial, credit or legal advice. Your actual figures depend on your lender’s or card issuer’s exact terms, fees, minimum-payment rules, interest calculation method and any changes they make. Check your statements and speak to a qualified adviser before making decisions. The avalanche order is chosen by APR only; we assume the payments, minimums and rates you enter stay fixed for the whole plan.

Page reviewed October 9, 2026 by the DebtWren team · Methodology · Changelog · Report an error