Debt Snowball vs. Avalanche Calculator

What this calculator answers

How long it takes to pay off several debts with one fixed monthly budget, and how much interest you pay, when you put everything above the minimums on the smallest balance first (snowball) or on the highest APR first (avalanche). Both are compared with paying only the minimums, and each plan comes with its payoff order, what to pay in each phase and a month-by-month schedule you can download.

How to use the debt payoff calculator

• Your debts: for each debt, the balance, the APR and the required minimum monthly payment, all from your latest statement. The name is optional; if you share a link, the names are part of it, so a nickname is enough. Add debt, Duplicate and Paste rows (from a spreadsheet: name, balance, APR, minimum) handle up to 15 debts, and the totals under the list add up the balances and minimums as you type.
• Budget entered as: choose whether your number is the total you can pay toward these debts each month, or the extra on top of the minimums. The line under the budget always shows the other one, so $900 in total reads as “$605.00 of minimums + $295.00 extra”.
• First payment date (optional): adds calendar months to the plan.

The Try buttons load the cases below: $200 more a month, no extra at all, a single card, and a minimum that doesn’t cover its interest. Save for comparison keeps up to three versions side by side, for example with and without a debt.

What is the debt snowball method?

You pay the minimum on every debt and put all the extra money on the smallest balance. When it is paid off, its payment moves to the next-smallest balance, so the amount “snowballs”. It clears whole debts early, so you see progress sooner, but it can cost more interest because a high-rate debt may wait.

What is the debt avalanche method?

You pay the minimum on every debt and put all the extra on the highest APR, then the next-highest, and so on. It aims the extra money at the debt that costs the most per dollar owed, which can save the most interest. The first debt can take longer to disappear.

How each month is calculated

• $I$ is a debt’s interest for the month, rounded to the cent.
• $B$ is its balance at the start of the month, and $r$ its APR as a decimal (21.99% is 0.2199).
• $T$ is your total monthly budget, and $\sum M$ the minimums of the debts still owed.
• $E$ is what goes to the focus debt on top of its own minimum. If that pays it off, the rest moves to the next debt in the same month.

The months repeat until every balance is zero. Because the budget stays the same, a paid-off debt’s minimum is never lost: it becomes part of $E$. With minimums only, nothing moves.

Worked example: four debts and $900 a month

1. Minimums: $50 + $60 + $185 + $310 = $605.00, so $900 leaves $295.00 extra a month.
2. Month 1 interest: Store card $1,900 × 27.99% ÷ 12 = $44.32; Visa $7,400 × 21.99% ÷ 12 = $135.605, rounded to $135.61; Car loan $12,300 × 6.9% ÷ 12 = $70.73; the medical bill charges none. Total $250.66.
3. Avalanche (Store card, Visa, Car loan, then the 0% medical bill): the Store card gets $355.00 a month and is gone in month 6. Visa then gets $540.00, and $590.00 from month 18 once the medical bill’s own minimum has cleared it in month 17. Visa is paid off in month 21 and the car loan gets the full $900.00 until month 29.
4. Snowball (Medical bill, Store card, Visa, Car loan): the medical bill gets $345.00 and is gone in month 3, the Store card gets $405.00 until month 8, Visa $590.00 until month 21, and the car loan $900.00 until month 29.

The avalanche saves $176.33, and both finish in the same month. The snowball pays off its first debt 3 months sooner (month 3 instead of 6) and clears two debts in the first year instead of one. Either plan saves more than $5,700 of interest compared with paying only the minimums ($5,973.17 with the avalanche, $5,796.84 with the snowball).

Snowball vs. avalanche: how much does the order change?

In the example, less than the budget does. The gap between the orders is $176.33 over 29 months, while adding $200 a month (the Add $200 a month button) finishes in 23 months with either order and cuts the avalanche’s interest to $2,517.27, $856.19 less. The snowball then pays $2,675.08, so the gap between the orders shrinks to $157.81.

The gap is larger when the biggest balance also has the highest rate, because the snowball then pays the most expensive debt last. The two orders give exactly the same plan when the smallest balance is also the highest rate all the way down the list, or when there is only one debt (One credit card: $7,400 at 21.99% with $400 a month takes 23 months and $1,720.44 of interest either way). They can also tie on cost when the orders differ, as with no extra money below.

What happens if you only pay the minimums?

Each debt is paid off on its own schedule, and a finished debt’s minimum is not moved to the others. In the example that takes 6 years 1 month and $9,346.63 of interest, and after 29 months $11,564.15 would still be owed.

Rolling the minimums over is worth a lot even with no extra money. With the budget at exactly the $605.00 of minimums (No extra, rollover only), both orders take 50 months and $7,731.98 of interest, 23 months and $1,614.65 less than minimums only. They tie here because the first minimum freed up, the medical bill’s, goes to the Store card in both orders.

When a minimum payment doesn’t cover the interest

If a minimum is at or below a month’s interest, paying only that minimum never shrinks the balance. In A minimum below its interest, the Store card’s minimum is $40, but its first month of interest is $44.32. The calculator warns about it, the line under that minimum says so as you type, and the minimums-only plan shows “Never”. The snowball and avalanche still pay it off, because extra money reaches it: the avalanche costs $3,373.46 as before, and the snowball, which leaves the Store card growing until month 3, costs $3,551.85.

If the whole budget can’t get ahead of the interest, the result says so instead of showing a date, along with the first month’s total interest, which the budget has to beat.

Reading the result

• The headline is the interest one order saves over the other, with the payoff time and first-payoff difference under it. When both orders cost the same, it shows the debt-free time instead.
• The three plans give each plan’s time, interest and total paid. The side-by-side table adds the interest each order saves compared with minimums only, the month of the first payoff and how many debts are paid off in the first year.
• Total owed, month by month charts the three plans. Open Chart data for the numbers.
• Plan details has a tab per plan: the payoff order with each debt’s month and interest, what to pay in each phase, and the full month-by-month schedule. Each table downloads as CSV.
• Months to debt-free and interest with a different extra amount reruns both plans with $50 to $500 more, or up to $200 less, extra a month, and shows the avalanche’s months and each order’s interest. In the example, $100 more ($395 extra) finishes the avalanche in 26 months (2 years 2 months) with $2,877.24 of interest, against $3,046.67 for the snowball. If an order would never finish at some amount, the note under the table says which.

Assumptions and limitations

• Interest is APR ÷ 12 on the balance at the start of each month. Card issuers often charge interest daily on the average daily balance, so statements will differ by a little.
• Minimums stay as entered. If a card’s minimum changes with the balance, its statement shows how long minimum payments alone would take.
• One APR per debt. A card with balances at different rates (purchases, a cash advance, a promotional transfer) is one debt here; the card issuer generally puts the amount above the minimum on the highest-rate balance first.
• No new charges, fees or rate changes. A 0% promotional rate is treated as 0% until that debt is paid off, even if the promotion would end sooner.
• The focus order is set once from the balances and APRs you enter. Ties go to the higher APR (snowball) or the smaller balance (avalanche), then to the order of the rows.
• The calculation runs for up to 100 years (1,200 months). It is an educational estimate, not financial advice.

Common mistakes

• Entering the extra where the total is meant, or the other way round. Check the line under the budget: it shows the minimums and the extra separately.
• Typing an APR as a decimal. The field is in percent, so 0.2199 means 0.2199%; the calculator points it out.
• Using the purchase APR for a promotional or cash-advance balance. Enter the rate that applies to that balance, and the rate after the promotion if it ends before the plan does.
• Lowering the payment when a debt is paid off. Both methods only work if the freed-up minimum keeps going to the next debt; paying the same total every month is the plan.
• Adding new charges to a card in the plan. The dates assume the balances only go down.