Enter each debt with its balance, rate and minimum payment. The calculator runs both common strategies - avalanche, which attacks the highest interest rate, and snowball, which clears the smallest balance first - and shows the real difference in months and interest rather than asserting that one is better.
Avalanche always costs less interest, because it kills the most expensive debt first. Snowball clears individual debts sooner, which many people find easier to sustain. The gap is often smaller than expected - frequently under a few hundred in interest - and a plan you actually follow beats an optimal one you abandon. The calculator shows your own numbers so it is a choice rather than a slogan.
Minimum payments are set so that most of each one is interest. Anything above the minimum goes almost entirely to principal, and that principal stops accruing interest immediately. On credit card debt an extra 100 a month routinely cuts years off the term.
Then the balance grows no matter what order you pay in, and the calculator says so rather than producing a schedule. That situation needs a different tool - a consolidation loan, a hardship arrangement with the lender, or debt counselling.