Amortization Schedule Explained: Why You Pay Mostly Interest at First

In the first payment on a 30-year, $300,000 mortgage at 7%, you pay $1,995.91. Of that, $1,750 goes to interest. Only $245.91 reduces your loan balance. After a full year of payments, you have paid $23,950 — and your balance has dropped by less than $3,000.

This is how amortization works, and it surprises almost everyone who sees it for the first time. Our amortization calculator generates the full schedule for any loan. This guide explains why it is structured this way and what you can do about it.

What amortization means

Amortization is the process of paying off a loan through regular scheduled payments over time. Each payment covers the interest that has accrued since the last payment, then applies anything remaining to reduce the principal balance. Because the balance is highest at the start of the loan, interest charges are also highest — leaving very little room for principal reduction in early payments.

As the balance slowly decreases, each payment covers slightly less interest and slightly more principal. This is why the balance barely moves for years, then seems to drop quickly near the end of the loan.

How each payment is calculated

The monthly payment on a fixed-rate loan is constant throughout the term. It is calculated using the amortized payment formula:

Payment = P x [r(1+r)^n] / [(1+r)^n - 1]

Where P is the loan principal, r is the monthly interest rate (annual rate / 12), and n is the total number of payments.

For a $300,000 loan at 7% over 30 years:

• Monthly rate: 7% / 12 = 0.5833%
• Number of payments: 360
• Monthly payment: $1,995.91

The amortization schedule: first year

Payment #	Payment	Interest	Principal	Remaining balance
1	$1,995.91	$1,750.00	$245.91	$299,754.09
2	$1,995.91	$1,748.57	$247.34	$299,506.75
3	$1,995.91	$1,747.12	$248.79	$299,257.96
6	$1,995.91	$1,742.77	$253.14	$298,508.51
12	$1,995.91	$1,736.06	$259.85	$297,032.39

After 12 payments and $23,950.92 paid, the balance is $297,032 — down only $2,968. The other $20,982 went entirely to interest.

The tipping point: when principal exceeds interest

On a 30-year mortgage at 7%, the crossover point — where your principal payment finally exceeds your interest payment — happens around payment 252: more than 21 years into the loan.

Year	Cumulative interest paid	Cumulative principal paid	Balance remaining
1	$20,983	$2,968	$297,032
5	$103,188	$16,757	$283,243
10	$201,285	$38,624	$261,376
15	$291,717	$67,173	$232,827
20	$371,609	$106,282	$193,718
25	$437,309	$159,582	$140,418
30	$418,527	$300,000	$0

Over 30 years, you pay $418,527 in interest on a $300,000 loan — you pay for the house more than twice. This is not a flaw or a scam. It is the mathematical consequence of borrowing a large amount for a long time. The alternative is a shorter loan term or a larger down payment.

Why 15-year mortgages save so much

A 15-year mortgage at 6.5% on the same $300,000:

• Monthly payment: $2,613 (vs $1,996 on the 30-year)
• Total interest paid: $170,342 (vs $418,527)
• Interest savings: $248,185

You pay $617 more per month but save nearly $250,000 in total interest. The 15-year also has a lower rate because lenders charge less for shorter-term risk. Use the mortgage calculator to compare 15 and 30-year options side by side with your actual numbers.

Extra payments: how they change the schedule

Because early payments are almost entirely interest, even small extra principal payments have a large impact on total interest paid. An extra $200/month on a $300,000 mortgage at 7%:

• Cuts the loan from 30 years to about 24 years
• Saves approximately $110,000 in interest
• Every extra dollar you pay reduces the principal balance, which directly reduces future interest charges

The key insight: extra payments made early in the loan are worth far more than extra payments made later, because they eliminate decades of future interest compounding on that reduced balance.

Comparing loan lengths: total cost

Loan term	Monthly payment	Total interest	Total cost
30 years at 7%	$1,996	$418,527	$718,527
20 years at 6.75%	$2,279	$246,915	$546,915
15 years at 6.5%	$2,613	$170,342	$470,342

Shorter terms get lower rates because lenders take on less long-term risk. The combination of lower rate and shorter compounding period creates disproportionate savings.

Amortization for car loans

Car loans amortize the same way, but the stakes are different because cars depreciate rapidly. On a 72-month auto loan, you may owe more than the car is worth for the first 3-4 years — a situation called being underwater or having negative equity. If the car is totaled in that window, your insurance payout may not cover what you owe.

This is why financial advisors recommend keeping auto loans to 48-60 months. Shorter terms mean less time underwater and less total interest paid.

How to read an amortization schedule

Each row in an amortization schedule shows:

• Payment number: which payment in the sequence
• Payment amount: fixed for the life of a fixed-rate loan
• Interest portion: balance x monthly rate
• Principal portion: payment minus interest
• Remaining balance: previous balance minus principal paid

Generate the full schedule for your loan with the amortization calculator — it shows every payment, the running interest total, and lets you model extra payments to see exactly how much you can save.