Monthly interest and payments
Each scenario starts with the balances, APRs, minimum payments, and plan start month you enter. The model accrues interest monthly at APR divided by 12, rounds each month's interest half-up to cents, then applies payments. Payments are capped at the amount due.
Minimums only, Snowball and Avalanche
The minimum-payments-only scenario uses each debt's minimum and does not use the extra-payment amount. Snowball applies extra money to the eligible debt with the lowest starting balance; Avalanche targets the eligible debt with the highest APR. Minimums are still included for every debt. Both strategies keep a fixed monthly budget (all minimums plus the extra amount), so the minimum freed when a debt is paid off rolls to the next target in the same month. The baseline does not roll freed minimums over.
What it does not model
This is a fixed-input estimate, not a lender's payment schedule. It does not model daily balances, changing rates or minimums, fees, missed payments, or retroactive promotional interest. A plan that does not finish within the 600-month simulation limit is reported as incomplete.