How Amortization Works: Where Each Payment Goes

Short answer: on a $400,000 loan at 7.18% fixed for 30 years, the payment is $2,709.74 a month — but payment number one is $2,393.33 of interest and only $316.41 of principal. The split reverses slowly: principal first exceeds interest after payment 240, total interest reaches $575,506, and an extra $100 a month toward principal saves $76,283 and clears the loan 39 payments early.

The loan we will follow

To make the mechanics visible, this article follows one loan from the first payment to the last. The numbers are illustrative, calculated with the standard amortization formula, and the assumptions are stated so you can check them:

• Loan amount: $400,000
• Rate: 7.18 percent fixed, the average 30-year fixed rate in Freddie Mac's Primary Mortgage Market Survey released November 5, 2026
• Term: 30 years (360 monthly payments)
• Monthly payment: $2,709.74, principal and interest only

That payment excludes property taxes, homeowners insurance, mortgage insurance, and HOA dues, which are real costs but sit outside the amortization schedule. The rate is a national average for conventional, conforming purchase loans to borrowers with 20 percent down and excellent credit; your quoted rate will differ. What does not differ is the shape of the schedule: on any fixed-rate loan, the interest share starts high and falls, and the principal share starts low and rises. The figures below are the result of that formula, not estimates.

Year 1: the payment is mostly the lender's

Payment number one is $2,709.74. Of that, $2,393.33 is interest — 88.3 percent — and $316.41 is principal. That is the whole story of the first year in one payment: the lender is paid first, because the interest charge is calculated on the full $400,000 balance, and only what is left over reduces what you owe.

By the end of year one, the picture has barely moved. Twelve payments total $32,516.87. Interest takes $28,592.53 of it — 87.9 percent — and principal takes $3,924.35. The balance stands at $396,075.65. You have lived in the house for a year, paid more than $32,000, and you own $3,924.35 more of it than the day you closed. That is not a trick. It is the formula doing exactly what it is designed to do: the lender's return is front-loaded, and your equity builds slowly at first.

This is also why the first years of a mortgage feel so unrewarding on a statement. The balance barely falls, and the monthly number never changes. Nothing is wrong with your loan. The schedule is working as written.

Year 5: five years in, you still owe 94 percent

Payment 60 tells the story of year five. Interest is $2,259.85 — 83.4 percent of the payment — and principal is $449.88, or 16.6 percent. The balance is $377,241.73, which is 94.3 percent of the original $400,000.

Add up the first five years and the scale of the split becomes hard to ignore. Sixty payments total $162,584.36. Interest accounts for $139,826.09. Principal accounts for $22,758.27. After five years of faithful payments, a borrower who started at $400,000 still owes $377,242.

Myth vs. math: "I have paid for five years, so I must own a good chunk of the house." The math says otherwise. Five years of payments equal 40.6 percent of the original loan amount — but 86 percent of that money went to interest, so the ownership share is only 5.7 percent. Time in the loan and equity in the house are not the same thing, and in the early years they barely move together. If you sell at year five, most of what you walk away with is the down payment and any price appreciation, not the principal you have paid down.

That is also why lenders care so little about how long you have had the loan when you ask to refinance, and so much about the current balance and the current value of the home.

Year 10: the turn is still slow

Payment 120 is the first one where the principal share is visible without squinting: interest $2,066.24 (76.3 percent), principal $643.50 (23.7 percent). The balance is $344,689.07.

Ten years, $325,168.72 paid in total, and the principal repaid is $55,310.93 — 13.8 percent of the original loan. Cumulative interest paid by this point is $269,857.79. You have now paid the lender more in interest than the house's remaining balance will be for several more years.

Myth vs. math: "My payment is fixed, so I am paying the loan down evenly." The payment is fixed; the split is not. The interest portion of each payment falls a little every month, and the principal portion rises by the same amount, because interest is always charged on the shrinking balance. In year one, each payment bought about $327 of principal on average. In year ten, each payment buys about $623. The payment never changed. What changed is the balance it is charged against — and that change compounds, slowly, in your favor.

Year 20: the crossover

Payment 240 is where the schedule finally tips. Interest is $1,393.17 — 51.4 percent — and principal is $1,316.57, or 48.6 percent. The next payment after it is the first in which principal exceeds interest. The balance is $231,525.86, and cumulative interest paid is $481,863.30.

Twenty years in, you have paid $650,337.44 in total — more than the loan itself — and you still owe $231,526. That sounds harsh, and it is the honest cost of a 30-year term at this rate: by the time the loan ends, total interest will be $575,506.16, or 144 percent of the amount borrowed. The house costs $975,506.16 in principal and interest before taxes, insurance, and upkeep.

Myth vs. math: "Extra payments mostly go to interest anyway, so there is no point." The opposite is true, and it is the most useful fact in this whole article. An extra payment goes entirely to principal, because the interest for the month is already covered by the regular payment. Adding $100 a month to this loan — $2,809.74 instead of $2,709.74 — pays it off in 321 months instead of 360 and saves $76,283.35 in interest. Adding $200 a month pays it off in 290 months and saves $132,202.74. The extra money never touches the interest column; it shortens the loan from the end, where the interest would have been heaviest. That is also why extra payments matter most early: a dollar of principal removed in year two saves interest in every one of the remaining 348 months.

Year 30: the last payment is almost all principal

Payment 360 is $2,709.74, of which $16.12 is interest and $2,693.62 is principal. The balance after it is zero. In the final year, interest totals just $1,230.10 while principal totals $31,286.77 — the mirror image of year one, when interest was $28,592.53 and principal $3,924.35.

The full arc, year by year, looks like this:

Read the table from top to bottom and the shape is unmistakable: the interest column shrinks every year, the principal column grows every year, and the two cross somewhere between years 19 and 20. Nothing about the loan changed. Only the balance did.

The decision rule

Knowing how the split works turns three common decisions into a rule you can apply to your own numbers.

Choose the shorter term when you can afford the payment and expect to stay. A 15-year loan at the November 5, 2026 PMMS average of 6.57 percent costs more per month but puts principal first much sooner — and because the rate is lower and the term is half, total interest is a fraction of the 30-year figure. The trade is real: a higher payment is a real commitment, and if it leaves you with no cash cushion, the cheaper monthly cost of the 30-year term is the safer choice.

Prepay principal when you have no higher-rate debt and a cash cushion already in place. Extra payments are the cheapest way to cut total interest, because they skip the interest column entirely. Even $100 a month on this loan saves $76,283. The rule is strict about order, though: credit card balances and other high-rate debt come first, and an emergency fund comes before extra mortgage payments. A prepaid mortgage does not pay a sudden repair bill.

Do not prepay when the money earns more elsewhere or you may need it soon. If you carry a balance on a card at 20 percent, that dollar saves more there. If you are saving for a move, a renovation, or a career change in the next year or two, keep the cash liquid. And if your mortgage rate is well below what a safe savings account pays, the math may favor holding the cash — check your own rate against current savings yields before deciding.

That is the whole of amortization: a fixed payment, a falling balance, and a split that moves a little every month until the last payment is almost entirely yours.

Sources

Consumer Financial Protection Bureau, "How does amortization work?" and related consumer guidance on mortgage amortization (amortization formula and the interest-first structure of fixed payments): https://www.consumerfinance.gov/ask-cfpb/what-is-amortization-en-1937/

Freddie Mac, Primary Mortgage Market Survey, released November 5, 2026 (30-year fixed average 7.18 percent; 15-year fixed average 6.57 percent): https://www.freddiemac.com/pmms

Amortization schedule figures in this article are illustrative calculations from the standard amortization formula using the stated assumptions ($400,000 loan, 7.18 percent fixed, 30 years, $2,709.74 monthly principal and interest payment, excluding taxes, insurance, mortgage insurance, and HOA dues), verified by computation.