Debt Snowball and Avalanche Calculator
Compare monthly debt payoff schedules using the smallest balance first or the highest annual rate first, with modeled interest and a month by month balance table.
Earlier editorial review
- Reviewed
- 2026-09-21
- Methodology
- 1.1
Sources
How it works
Enter every debt with its name, balance, annual percentage rate, and required minimum payment. The starting budget includes minimums only for debts with positive balances. Add the amount available above those minimums. Use one currency and enter 24 for a 24% annual rate.
The calculator sets the monthly budget to all starting minimums plus the extra amount. Each month it adds one twelfth of the entered annual rate as interest, pays minimums, and applies the remaining budget to the selected target.
Snowball selects the smallest remaining balance. Avalanche selects the highest remaining annual rate. When a balance is cleared, the remaining payment budget moves to the next eligible debt and the initial budget stays fixed.
Compare modeled interest, months, and the monthly balance table. A result still unpaid after 1200 months is shown as unpaid at the limit. Update the inputs when a balance, rate, minimum, or available payment changes.
Step by step
- Enter balances, annual rates, minimums, and one extra monthly amount.
- Compare the two schedules using the same inputs and currency.
- Review the monthly balances and check whether either schedule reaches zero within the limit.
Worked example
Enter a card balance of 5000 at 24% APR with a minimum payment of 150, and a loan balance of 3000 at 8% APR with a minimum payment of 75. Add 200 per month. The starting budget is 425 per month. Under this model, snowball pays off in 23 months with 1769.10 interest. Avalanche pays off in 22 months with 1274.80 interest.
For these inputs, avalanche produces 494.29 less modeled interest and finishes one month earlier. The results can change with the balances, rates, minimums, and extra payment. If both rules select the same debt order, their schedules can match. Reproduce the inputs above, then change one amount to see its effect.
Using the comparison
Use the comparison to see how two target ordering rules affect interest and time under the same fixed monthly budget. The modeled difference depends on the balances, rates, and minimums you enter.
Check account statements and payment terms for actual rates, due dates, fees, and required amounts. This schedule does not contact creditors or account for circumstances outside its listed assumptions.
Common input mistakes
Use the amount currently owed, not the credit limit. Enter the annual rate as a percentage, so 24 means 24%, not 0.24. Use the required monthly minimum rather than the full statement balance.
Include only minimum payments for debts with positive balances in the starting budget. Do not treat an unpaid balance at the 1200 month limit as paid off.
Calculation method
Starting monthly budget = minimum payments on positive balance debts + extra monthly amount
For each month:
1. Interest = current balance × annual rate ÷ 12 ÷ 100
2. Add interest to each positive balance
3. Pay each active debt up to its minimum from the fixed budget
4. Apply remaining budget to the priority debt
5. If that balance reaches zero, move remaining budget to the next priority
Snowball priority: smallest current balance
Avalanche priority: highest current annual rate
The starting monthly budget includes the minimum payments on debts with positive balances plus the extra amount. It remains fixed as those debts close. A cleared debt no longer receives a payment, so its unused minimum is available for other balances. Interest is added before payments once per modeled month. The simulation stops at 1200 months and reports unpaid balances rather than counting them as paid off.
Assumptions and limits
This is a simplified monthly model. It applies a fixed annual rate divided by 12 before payments, keeps the starting monthly budget constant, and assumes payments are made as entered. It does not model daily interest, variable rates, changing minimum formulas, purchases, late fees, promotional expiration, deferred interest, penalties, settlements, taxes, or creditor specific allocation rules. Inputs must produce finite numeric results; calculations outside the supported numeric range are reported as unavailable. A 1200 month limit is applied, and remaining debt is not treated as paid off.
Key terms
- Debt snowball
- A payoff rule that directs the remaining monthly budget to the active debt with the smallest balance after minimum payments.
- Debt avalanche
- A payoff rule that directs the remaining monthly budget to the active debt with the highest annual rate after minimum payments.
- Monthly payment budget
- The sum of the starting required minimum payments and the extra monthly amount, held constant as debts close.
Related tools
Use the Latte Factor calculator to estimate a recurring amount you could assign to debt payments. Return here to compare how that amount changes the modeled schedules.
The Mortgage Overpayment calculator models a separate secured loan. This debt comparison accepts a list of balances and does not assess which account should take priority in your circumstances.
FAQ
What information does the calculator need?
Enter each debt name, current balance, annual percentage rate, and required monthly minimum. Enter an extra monthly amount that is available after those minimums. All balances and payments must use the same currency.
How does the monthly interest calculation work?
Each month the model adds interest using the entered annual rate divided by 12, then applies minimum payments and the remaining budget. It treats that rate and each minimum as fixed for the full simulation.
What happens to a minimum payment after a debt is paid?
Both schedules use a fixed monthly budget equal to the starting minimum payments on positive balance debts plus the extra amount. When an active debt is cleared, its minimum remains in that budget. Any remaining money can move to the next debt during the same month.
How do the two payoff rules differ?
Snowball targets the smallest current balance. Avalanche targets the highest current annual rate. Equal priorities are resolved by the other measure, then by the order the debts were entered. The comparison describes this model and does not determine which approach fits a person's budget or preferences.
Can I check a numerical example?
For the example, the minimums are 150 and 75, and the extra amount is 200, so the fixed starting budget is 425. At the displayed rates and balances, snowball takes 23 months and accrues 1769.10 interest. Avalanche takes 22 months and accrues 1274.80. The worked example and tests use the same inputs.
Related tools
The Latte Factor calculator can model a recurring amount, while Mortgage Overpayment handles one secured loan. Use their separate results only when the inputs and assumptions match the question you are considering.