Mortgage Amortization Explained: How Your Payments Are Split
A mortgage payment looks level, but its composition is not. In the first years most of each payment is interest; in the last years most is principal. That split — the amortization schedule — decides how much equity you build, how much interest you pay, and why extra payments early in the loan are worth far more than the same payments later.
The schedule, in numbers
Take a $400,000 loan at 6.5% for 30 years. The payment is $2,528 a month. The first payment sends $2,167 to interest and $362 to principal. After 10 years the balance is still about $354,000 — you have paid $303,000 and reduced the debt by $46,000. Half the loan is repaid only around year 19. Total interest over the full term: roughly $510,000, more than the house cost.
This is not a trick by the lender; it is arithmetic. Interest each month is the current balance times the monthly rate. A large balance charges large interest, leaving little of a fixed payment for principal. As the balance falls, the interest share falls with it, and the same payment retires more debt. The schedule is front-loaded because the balance is.
What extra payments change
An extra $200 a month on that loan pays it off about 5 years early and saves roughly $113,000 of interest. Extra payments work because every dollar goes entirely to principal, and a dollar of principal removed in year 2 would otherwise have charged interest for the remaining 28 years. The same $200 started in year 20 saves a fraction as much. If you plan to prepay, earlier is worth more — but keep the emergency fund and higher-interest debt ahead of the mortgage in the queue.
- Biweekly half-payments equal one extra payment a year — worth about 4–5 years off a 30-year loan at typical rates.
- A lump sum (bonus, tax refund) applied to principal has the same effect as many small extras.
- Check for prepayment penalties before sending large extras; they are uncommon on modern US mortgages but exist.
Questions, answered
Does a shorter term or extra payments save more?
A 15-year term usually carries a lower rate and forces faster payoff, saving the most interest — but it commits you to the higher payment. Extra payments on a 30-year loan save slightly less yet stay optional in a hard month.
Why is my payoff amount higher than my balance?
The payoff figure adds interest accrued since the last statement and any fees. The balance is the principal only.
Reviewed by Tahir Shehzad, ACMA. Figures are reviewed against the sources on our methodology page. This guide is education, not personal financial advice.