amortization

Every fixed-rate loan — mortgage, car, student — runs on the same engine: a constant payment whose mix flips over time from mostly interest to mostly principal. The simulator splits each payment into the slice that pays the bank and the slice that pays the debt, then lets you add an extra payment and watch years of interest disappear.

A credit card is a loan whose required payment shrinks as your balance does — so progress slows every single month, by design. The simulator races the minimum-payment path against a fixed payment you choose: the same $5,000 balance takes 26 years one way and under 5 the other. Drop the minimum a notch and it never pays off at all.

When you owe on several debts at once, the only real decision is which one gets your spare dollars first. Avalanche (highest rate first) is mathematically optimal; snowball (smallest balance first) hands you a paid-off debt far sooner and keeps you motivated. The simulator runs both orderings on the same debt mix and budget: on the default $25,000 mix, avalanche saves $3,792 — and snowball's first win arrives 15 months earlier.

You've got a couple of cards in the mid-20s% and a personal loan, and a lender offers to roll them all into one new loan at a single, lower rate. One payment instead of three, and the rate is better than any of your cards — what's not to like? The catch is the same one that trips people up on mortgage refinances: the new loan usually runs LONGER than it would have taken to pay the debts off separately, and stretching the balance over more months can add up to more total interest even at a lower rate. There's a second, quieter cost too — folding several balances into one erases the finish line on whichever debt was closest to gone, so the relief of almost being done with your worst card resets to zero. This lesson races 'keep them separate' against 'consolidate' on the same chart, so you can see exactly when the lower rate is a real win and when it's a longer, costlier version of the same debt.

You're carrying a high-rate card balance, and a new card offers 0% interest for the next 15 months if you move the debt over — for a one-time fee. It sounds like a free pause on interest, and for a while, it is. But that 0% is a countdown, not a discount: the day the promo window closes, whatever's left starts accruing at a normal — often steep — ongoing rate. This lesson races the transfer against just leaving the balance on your original card, so you can see exactly when the 0% offer is free money and when the fee plus the reverted rate quietly cost you more than doing nothing ever would have.