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How Loan Amortization Works (With Examples)

Amortization is how a fixed monthly payment pays off a loan by a set date. Each payment first covers the interest on what you still owe, and the rest lowers your balance, so a bigger share goes to principal every month.

What amortization means

To amortize a loan is to pay it off bit by bit, with equal payments, by a set end date. Most fixed-rate mortgages, car loans and personal loans work this way. Every payment does two jobs:

1. It pays the interest charged since your last payment, based on the balance you still owe.
2. The rest pays down the principal, the amount you borrowed. A lower balance means a little less interest next month, so a little more of the next payment goes to principal.

A table listing every payment and its split is called an amortization schedule. Only the principal part lowers your balance and builds equity. If your mortgage payment includes escrow for property taxes and insurance, that money isn't part of the amortization. Your monthly statement shows how much went to principal, interest and escrow.

The amortization formula

Lenders use a standard formula to find the payment that pays off the loan exactly at the end of the term:

M = P × r(1 + r)ⁿ ÷ [(1 + r)ⁿ − 1]

Here M is the monthly payment, P is the amount borrowed, r is the monthly interest rate (the annual rate ÷ 12) and n is the number of monthly payments. At a 0% rate, the payment is simply P ÷ n. Then every month follows the same three steps:

1. Interest = balance × r
2. Principal = payment − interest
3. New balance = old balance − principal

Example: for a $25,000 car loan at 7% for 60 months, P = 25,000, r = 0.07 ÷ 12 and n = 60. The formula gives a payment of $495.03. In month 1, interest is $25,000 × 0.07 ÷ 12 = $145.83. The other $349.20 goes to principal, so the balance falls to $24,650.80. Month 2 starts from that new balance.

Example: a $25,000 car loan, month by month

Here are the first 12 payments on that loan. It's the default example in our loan calculator, so you can open it to see all 60 months or try your own numbers.

• The payment never changes, but each month about $2 more goes to principal and $2 less to interest.
• On this short loan, principal leads from the start. Interest is 29.5% of the first payment and just $2.87 of the last one.
• Interest adds up to $1,612.91 in the first year and $4,701.80 over all 60 months.

Example: a $320,000 mortgage, year by year

Now take a 30-year, $320,000 mortgage at 6.5%: a $400,000 home with 20% down. The formula gives a principal-and-interest payment of $2,022.62 a month, or $24,271 a year. It's the default example in our mortgage calculator, before taxes and insurance. Here's the split in selected years, rounded to the dollar. The last column shows how much of that year's payments went to principal.

Show all 30 years

Every year of a $320,000, 30-year mortgage at 6.5%

Year	Principal paid	Interest paid	Ending balance	Share to principal
1	$3,577	$20,695	$316,423	15%
2	$3,816	$20,455	$312,607	16%
3	$4,072	$20,200	$308,535	17%
4	$4,345	$19,927	$304,191	18%
5	$4,636	$19,636	$299,555	19%
6	$4,946	$19,325	$294,609	20%
7	$5,277	$18,994	$289,332	22%
8	$5,631	$18,641	$283,701	23%
9	$6,008	$18,264	$277,694	25%
10	$6,410	$17,861	$271,284	26%
11	$6,839	$17,432	$264,444	28%
12	$7,297	$16,974	$257,147	30%
13	$7,786	$16,485	$249,361	32%
14	$8,308	$15,964	$241,053	34%
15	$8,864	$15,407	$232,189	37%
16	$9,458	$14,814	$222,732	39%
17	$10,091	$14,180	$212,641	42%
18	$10,767	$13,505	$201,874	44%
19	$11,488	$12,784	$190,386	47%
20	$12,257	$12,014	$178,129	51%
21	$13,078	$11,193	$165,051	54%
22	$13,954	$10,317	$151,097	57%
23	$14,888	$9,383	$136,208	61%
24	$15,886	$8,386	$120,323	65%
25	$16,949	$7,322	$103,373	70%
26	$18,085	$6,187	$85,289	75%
27	$19,296	$4,976	$65,993	79%
28	$20,588	$3,683	$45,405	85%
29	$21,967	$2,305	$23,438	91%
30	$23,438	$833	$0	97%

Over the full 30 years you'd pay $408,142 in interest, about 127.5% of the amount borrowed. For a real loan offer, the Loan Estimate shows this measure as the Total Interest Percentage (TIP).

Why early payments are mostly interest

Each month's interest is your balance times the monthly rate. At the start, the balance is as high as it will ever be, so interest takes most of the payment. On the mortgage above, the first payment is 85.7% interest: $1,733.33 to interest and $289.28 to principal. As the balance falls, the interest charge shrinks, and more of the same payment is left for principal.

So interest isn't front-loaded as a penalty: you pay it only on what you still owe, and early on you owe the most. On a long loan, though, the shift is slow:

• Principal first tops interest with payment 233, 19 years and 5 months in.
• After 5 years you'd have paid $121,357, but only $20,445 of it went to principal. You'd still owe $299,555.
• You don't owe less than half the original amount until payment 257, more than 21 years in.

This matters if you might sell or refinance. The CFPB notes that borrowers keep a mortgage for about five years on average before moving or refinancing. The "In 5 years" line in the Comparisons section of a Loan Estimate shows how much principal you'd have paid off by then.

Shorter terms and lower rates shift faster. On the car loan, principal is the bigger share from the first payment. The same $320,000 over 15 years costs $2,787.54 a month, and principal overtakes interest with payment 53, 4 years and 5 months in. Our guide to 15-year vs. 30-year mortgages compares the two.

How extra payments change the schedule

Extra money that's applied to principal lowers your balance right away. Every later month then charges interest on a smaller balance, so the savings build over time. On most loans the required payment stays the same, and the loan simply ends sooner. Here's the effect on the $320,000 mortgage:

On the $25,000 car loan, an extra $50 a month pays it off 6 months sooner and saves $522.62 in interest. Extra money helps most early in a loan, as the FAQ below shows. Before you start:

• Make sure it goes to principal. Tell your servicer the extra amount is for principal, then check your next statement to see how it was applied.
• Check for a prepayment penalty. Not all loans have one, and the CFPB says small extra principal payments on a mortgage usually don't trigger one. A mortgage Loan Estimate says YES or NO next to "Prepayment Penalty."
• Watch for precomputed interest. This method is uncommon on car loans. With it, the total interest is set at the start, so extra payments don't reduce it, though paying off early may earn you a refund of some "unearned" interest.

To test extra, lump-sum or biweekly payments on your own mortgage, use our mortgage payoff calculator.

Amortizing loans vs. other kinds of debt

Not every kind of debt pays itself off on a schedule. Here's how the main types compare:

Interest-only loans

Payments cover only the interest for a set period, so the balance doesn't go down. When the period ends, the payment rises even if the rate doesn't, because the principal must now be repaid over fewer years. If the $320,000 loan at 6.5% were interest-only for 10 years, you'd pay $1,733.33 a month and still owe $320,000 after a decade. The payment would then jump to $2,385.83 for the last 20 years, about $363 more than the regular payment. Total interest would reach $460,600, or $52,458 more than the regular loan. Some home equity lines of credit (HELOCs) also allow interest-only payments while you can still draw on the line.

Revolving credit: credit cards and HELOCs

You can borrow, repay and borrow again up to a limit, so there's no schedule that ends at $0. On many cards the minimum payment shrinks with the balance, which stretches repayment out. Paying a fixed amount with no new charges makes a card behave like an amortizing loan: on a $5,000 balance at 22% APR, $200 a month clears it in 2 years 10 months with $1,749.88 of interest. Paying only a minimum of 1% of the balance plus interest (at least $25) would take 19 years 2 months and cost about $8,100. Try your own card in our credit card payoff calculator.

Negative amortization

If a payment doesn't cover the interest due, the unpaid interest is added to the balance, so you owe more even though you're paying. Some payment-option mortgages allowed this. On the $320,000 loan at 6.5%, the first month's interest is $1,733.33, so a $1,500 payment would add $233.33 to the balance. After a year you'd owe $322,885 despite paying $18,000, and after five years you'd owe $336,491. Payments usually rise sharply later, and you could end up owing more than the home is worth.

Under CFPB rules, a "Qualified Mortgage," a category of home loans with more stable features, can't have an interest-only period or negative amortization.

"Amortization" in accounting means something else

In business accounting and taxes, amortization means spreading certain costs over several years, much like straight-line depreciation. Examples are the price of goodwill and other intangible assets a business buys, or the costs of starting a business. The IRS generally requires businesses to amortize goodwill and certain other purchased intangibles over 15 years, and amortization is reported on Form 4562. That's the meaning on a company's financial statements, not loan payments.

Frequently asked questions

This guide is general education, not financial advice. Our examples assume a fixed rate, interest charged monthly at one-twelfth of the annual rate, on-time payments and no fees, taxes or insurance. Figures are rounded for display. See our terms of use.

Last reviewed: October 2026