Debt Snowball Calculator
Calculate your debt payoff timeline with the debt snowball and avalanche methods to see when you'll become debt-free and how much interest you can save.
How to Use This Calculator
Paying off multiple balances feels overwhelming when payments are scattered across different cards and loans. This calculator puts every balance into a single clear timeline:
- List your current debts: Enter the name, current balance, interest rate (APR), and required minimum monthly payment for each credit card or loan.
- Add an extra monthly payment: Decide how much additional cash you can comfortably commit beyond your minimum payments each month. Even an extra $50 or $100 accelerates your payoff date significantly.
- Choose your payoff strategy: Switch between the Debt Snowball (paying smallest balances first for fast psychological wins) and Debt Avalanche (tackling highest interest rates first to save money).
- Follow the roll-forward milestones: As each balance reaches zero, its payment rolls into the next debt in line until you're completely debt-free.
The Formula & Compounding Mechanics
Each individual debt generates interest on its outstanding balance every month according to its monthly periodic rate. The monthly interest charge is calculated as:
When you make your monthly payment, the lender deducts this monthly interest charge first, and only the remaining portion reduces your principal balance:
The roll-forward mechanic is where the snowball builds momentum. Your total monthly debt budget remains fixed throughout the entire timeline:
In month one, you pay the minimum on every debt, while directing all remaining funds from your debt budget to your #1 target debt. Once that target debt hits a zero balance, you don't reduce your monthly spending. Instead, its minimum payment stays in your debt budget and rolls directly into target debt #2. Your payments against each subsequent loan grow larger without requiring any additional money from your pocket.
Worked Example: Snowball vs. Avalanche
Consider a realistic household with three separate consumer debts and a plan to put an extra $150 per month toward becoming debt-free:
- Store Card: $1,000 balance at 12% APR (Minimum: $40/month)
- Credit Card: $4,000 balance at 24% APR (Minimum: $120/month)
- Car Loan: $8,000 balance at 6% APR (Minimum: $180/month)
The total required minimum payment across all three accounts is $340 per month ($40 + $120 + $180). Adding the $150 extra payment gives a fixed monthly debt budget of $490 per month.
Under the Debt Snowball strategy:
- The Store Card has the lowest balance ($1,000). It receives its $40 minimum plus the entire $150 extra payment ($190 total). It gets wiped out in Month 6 with just $32.64 in total interest paid.
- In Month 7, that $190 rolls into the Credit Card ($120 minimum + $190 snowball = $310/month). The Credit Card is eliminated in Month 20.
- In Month 21, the entire $310 rolls into the Car Loan ($180 minimum + $310 = $490/month). The Car Loan is eliminated in Month 31.
Total interest paid under Snowball is $1,854.67 over 31 months.
Under the Debt Avalanche strategy:
- The Credit Card has the highest APR (24%). It receives its $120 minimum plus the $150 extra ($270 total). It gets paid off in Month 18.
- In Month 19, the $270 rolls into the Store Card (12% APR), knocking it out by Month 20.
- In Month 21, the full $490 attacks the Car Loan, wiping it out in Month 31.
Total interest paid under Avalanche is $1,723.28 over 31 months. Both methods reach the finish line in Month 31, but the Avalanche saves $131.39 in cash by targeting the 24% card immediately. I'm a numbers guy by habit, so on paper I always lean toward the Avalanche—why hand the bank an extra dollar if you don't have to? But seeing that first account balance hit flat zero in Month 6 does something to your brain that a spreadsheet can't replicate. That quick win gives you proof that the plan actually works.