What Is an Amortization Schedule? How Your Loan Payments Work

An amortization schedule is a table that shows exactly how each loan payment is divided between principal and interest over the full life of the loan. It maps out every single payment — whether that is 60, 180, or 360 payments — showing you the gradual shift from paying mostly interest to paying mostly principal.

On a typical 30-year, $300,000 mortgage at 7%, your first monthly payment of $1,996 breaks down as $1,750 toward interest and only $246 toward principal. By year 15, the split flips: $1,057 goes to principal and $939 to interest. In the final year, nearly the entire payment goes to principal. Understanding this schedule explains why the early years of a mortgage feel like you are barely making progress on the balance.

How Amortization Works

Each month, your lender calculates interest on the outstanding balance. On a $300,000 loan at 7% annual rate, the first month's interest charge is $300,000 × (7% / 12) = $1,750. Your fixed payment is $1,996, so $1,996 - $1,750 = $246 goes toward reducing the principal balance. The new balance becomes $299,754.

In month two, interest is calculated on $299,754 instead of $300,000, so the interest portion drops slightly to $1,749 and the principal portion rises to $247. This pattern continues for every payment. The monthly amount stays the same, but the interest shrinks and the principal grows with every payment. By the final payment, you owe almost nothing in interest.

Why Early Payments Are Mostly Interest

Lenders do not front-load interest as a penalty. It is pure math: interest is always calculated on the remaining balance. When the balance is large (at the start of the loan), the interest charge is large. As the balance shrinks, so does the interest. On a $300,000 mortgage at 7% for 30 years, you pay $415,608 in total interest — more than the original loan amount. About 60% of the total interest is paid in the first half of the loan term.

This front-loading effect is why refinancing in year 10 of a 30-year mortgage essentially restarts the clock. You have already paid the majority of the interest-heavy payments and are finally making real progress on the principal. Refinancing into a new 30-year loan puts you back to square one in the amortization curve.

The Impact of Extra Payments

Extra payments go directly to principal, which has a compounding effect on savings. On a $300,000 mortgage at 7% for 30 years (monthly payment: $1,996), adding just $200 per month to principal cuts the loan term from 30 years to about 22.5 years and saves roughly $130,000 in interest. That is a $130,000 return on $54,000 in extra payments.

Even one extra payment per year — either as a lump sum or divided into 12 slightly higher monthly payments — can shave 4-5 years off a 30-year mortgage. The amortization schedule makes this visible: each extra principal payment reduces every future interest charge for the remaining life of the loan.

How to Read an Amortization Schedule

A standard amortization schedule has five columns: payment number, payment amount, interest portion, principal portion, and remaining balance. Some schedules include cumulative totals for interest and principal paid. Look at three key points: the first payment (to see how much goes to interest), the crossover point (where principal exceeds interest for the first time), and the total interest line at the bottom.

For a $300,000 mortgage at 7% for 30 years, the crossover point — where you start paying more toward principal than interest in each payment — does not arrive until about year 18. For the first 18 years, more than half of every payment goes to interest. The crossover point arrives sooner with shorter loan terms: on a 15-year mortgage, it happens around year 5.