Loan Amortization Schedule Explained: Where Your Payment Goes

The first payment on a $400,000 mortgage at 6.7% is $2,581. Of that, $2,233 is interest and $348 is principal. In month one, your home's debt falls by less than the cost of a new couch. Thirty years later, the same payment is almost all principal. That swap is amortization, and it decides what every fixed-rate loan you hold actually costs.

This guide explains the schedule row by row, shows where the interest goes in year one versus year twenty-nine, and covers what prepayment does to the table.

What an amortization schedule is

An amortization schedule is the complete table of payments on a fixed-rate loan. Every row splits one payment into interest and principal, shows the running balance, and the last row totals the interest paid over the whole term. Lenders are required to provide it for most consumer loans, and it answers the question the monthly bill hides: where does the money go?

The schedule exists because fixed payments and falling balances do not line up. The payment stays level while the balance shrinks, so the split has to change every month.

Why interest is front-loaded

Interest is charged on the outstanding balance, and the balance is largest on day one. Early payments therefore carry the most interest and the least principal. Each payment lowers the balance, the next payment's interest share shrinks, and the principal share grows. The process is gradual for years, then accelerates sharply near the end.

The schedule is not a penalty. The total interest on the table is the same simple-interest math the loan was priced with. What the schedule adds is timing: the interest is concentrated in the first half of the term, which is why the first years of a mortgage build so little equity.

The schedule in three rows

Here is the computed $400,000 loan at 6.7% over 30 years:

All figures are computed and rounded. The pattern is the point: after fifteen years of payments, the balance has fallen from $400,000 to roughly $292,600, and the payment still carries more interest than principal. In year twenty-nine, the split finally flips hard toward principal.

The same shape on every loan

The schedule does not change its shape with the loan size. A car loan amortizes the same way: the first payments are interest-heavy, and the balance falls slowly until late in the term. On a computed $15,000 car loan at 6%, month one carries about $75 of interest, and the last payments are almost all principal. The difference is scale, and the lesson is identical — the early months are the expensive ones, which is when extra payments do the most work. The early loan payoff calculator applies the schedule to loans of any size.

The 15-year option

Term choice is a schedule choice. The same $400,000 at 6.7% over 15 years computes to about $3,529 a month and about $235,166 of total interest, against about $529,160 over 30 years. The shorter term saves roughly $294,000 of interest at the cost of about $948 more per month. The two schedules show both futures side by side, and the choice is a cash flow decision rather than a math one.

How to read your own schedule

Every schedule has the same four columns, and each one answers a question:

• Payment number. The row index, and a quiet reminder of how many remain.
• Interest. What the lender keeps this month. Add the column and you get the true cost of the loan.
• Principal. What your equity gains this month. This column grows every row.
• Remaining balance. What you still owe after the payment. Month one on the example drops the balance by $348, which explains why early payoff discussions start with this column.

The mortgage payment breakdown guide shows the other half of the picture: the escrow line for taxes and insurance that rides on top of principal and interest in your actual bill.

What prepayment does to the schedule

An extra payment reduces principal, and every principal dollar skips the interest it would otherwise carry for the rest of the term. On the computed mortgage, one extra payment in year one removes roughly $2,581 of principal plus the interest that balance would have generated over twenty-nine years. The mortgage extra payment calculator prints the revised schedule, the earlier payoff date, and the interest saved, which runs to five figures on a loan this size.

The decision to prepay is separate from the math. The mortgage early payoff guide weighs the liquidity, tax, and investment tradeoffs before you send the extra money, and the early loan payoff calculator applies the same logic to smaller loans.

Why refinancing restarts the clock

A refinance pays off the old loan and opens a new one, which means a new schedule with interest front-loaded again. The rate cut has to outweigh the restart, because the first years of the new loan repeat the interest-heavy pattern the old loan already worked through.

The correct comparison is total interest under both schedules, not the monthly payment. A lower payment over a longer new term can cost more overall, and the schedule is the only place that shows it.

Run the numbers

The loan amortization schedule calculator builds the full table for any amount, rate, and term, and adds extra-payment scenarios. Enter your actual loan, read the year-one rows, and then test one extra payment. The banking and borrowing calculators cover the rest of the debt family.

Read any loan as a schedule, and the expensive months stop being a surprise. The first payment is the most interest-heavy payment you will ever make on that loan, and the table shows exactly why.