| Payment | Scheduled payment | Extra payment | Interest paid | Principal paid | Ending balance | No-extra balance |
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What is debt?
Debt is money you owe to someone else, usually a bank or lender. In return for getting the money up front, you agree to pay it back over time plus an extra fee called interest. Mortgages, car loans, student loans, and credit cards are all forms of debt.
Principal vs. interest
The principal is the amount you originally borrowed. Interest is the cost the lender charges you for using their money. Every payment you make is split between these two things. Early in a loan, most of each payment is interest. Later in a loan, most of each payment is principal.
How amortization works
Amortization is the schedule that splits each payment into interest and principal. Interest each month is calculated on your current balance, so as the balance falls, less of each payment goes to interest and more goes to principal. This is why paying down the balance faster causes the interest portion to shrink quickly.
The "No-extra balance" column on this page shows what your balance would have looked like with no extra payments, so you can see the gap your extra payments create.
Why extra payments help so much
When you pay extra toward a loan, every dollar of extra payment goes straight to principal. That dollar then stops accruing interest for the rest of the life of the loan. On a 30-year mortgage at 7%, a single extra $100 payment in year one saves more than $700 in interest over the remaining life of the loan.
The benefit of extra payments is largest on high-interest debt and on loans with many years left. Each extra dollar paid early skips many years of interest.
Interest rate matters a lot
A high interest rate makes debt much more expensive. A $20,000 car loan at 4% over 5 years costs about $2,100 in interest. The same loan at 10% costs about $5,500. Higher rates mean more of your money goes to the lender instead of paying off what you owe.
Minimum payment trap
Many loans, especially credit cards, allow very low minimum payments. Paying only the minimum can keep you in debt for decades and cost more in interest than the original purchase amount. Even a small amount above the minimum can shorten the payoff dramatically.
Good debt and bad debt
Not all debt is equal. A low-rate mortgage or student loan can be reasonable if it helps you build long-term value. High-rate credit card debt is almost always worth paying off as fast as possible. Looking at the interest rate is usually the fastest way to tell whether debt is helping or hurting you.
Common misconceptions
People often assume that lower monthly payments mean a cheaper loan. They do not. Stretching a loan over more years lowers the monthly payment but usually increases the total interest paid. A shorter term with a higher monthly payment usually costs less overall.
Key takeaway
The faster you reduce a loan balance, the less interest you pay. Extra payments early in the loan are the most powerful because they remove principal that would have been earning interest for the lender for years. Even modest extra payments, made consistently, can save thousands of dollars and shorten a loan by years.