Debt payoff is a month-by-month process, and guessing at the total misleads. The Debt Snowball Calculator simulates both payoff methods in parallel: each month it adds interest to every balance, collects the minimum payments, applies your extra to the target debt, and when a debt retires, that minimum frees up for the next target. Everything runs in the browser, no balance is uploaded anywhere.
Three default debts totalling 45,000
The tool opens with three debts: a credit card at 5000 with 18 percent and a 150 minimum, a car loan at 15000 with 6 percent and a 300 minimum, and a student loan at 25000 with 5 percent and a 250 minimum. Together they total 45,000 in principal. The monthly rate is the annual rate divided by 12, so 18 becomes 1.5 per month. The three minimums add to 700, and with the default 200 extra payment the plan commits 900 every month. A credit card is often the first debt to die, and the Credit Card Payoff Calculator models that single balance on its own.
Why the two methods tie on the defaults
Snowball pays the smallest balance first; avalanche pays the highest rate first. On the defaults both orderings line up: 5000 is both the smallest balance and the highest rate. The two simulations finish identically in 58 months, with 6,487.76 of interest and 51,487.76 total paid, which is exactly 45,000 plus the interest. The credit card retires in month 17, the car loan in month 35, and the student loan in month 58. Because avalanche cannot claim a lower interest figure, the winner badge credits snowball with the psychological boost of clearing a debt early.
What the 200 extra payment is worth
Set the extra to zero and the same three debts take 78 months, with 9,778.53 of interest. The 200 extra payment cuts that to 58 months and 6,487.76, saving 20 months and 3,290.77 of interest, and it pulls the credit card payoff forward from month 47 to month 17. For a single amortized loan the same arithmetic lives in the Loan Calculator, and the APY/APR Converter is where you check the rate you type before the plan inherits it.
When the methods diverge: 538.46 to avalanche
Give the tool a small 3000 balance at 4 percent with a 100 minimum and a 10000 balance at 18 percent with a 150 minimum, keeping the 200 extra. Snowball attacks 3000 first and finishes in 38 months with 3,839.71 of interest, retiring the small debt in month 11. Avalanche attacks the 18 percent first, finishes in 37 months with 3,301.25 of interest, and saves 538.46. The snowball still delivers an early win in month 11, which is the trade the method is known for.
The 600-month cap and the red banner
The simulation stops at 600 months, fifty years, and if interest outpaces the payments it flags the result as unpayable with a red banner instead of a payoff date. Put 10000 at 24 percent with a 200 minimum and no extra: the monthly interest is exactly 200, the balance sits flat at 10000 for all 600 months, and no date ever arrives. Clearing debt assumes a buffer, which the Emergency Fund Calculator sizes before you redirect cash, and a Savings Goal Calculator says what the freed minimums become once the last debt retires.
Where the numbers go next
The month-by-month table is the heart of the credit card payoff guide, which works the same formula out on one balance, and the buffer it should sit next to comes from the emergency fund guide. Run the defaults, flip the rates so the orderings disagree, and read both badges before you pick a method.