Amortization is the schedule that turns a large loan into a series of equal monthly payments that bring the balance to zero by the end of the term. Understanding it explains why your balance falls slowly at first, why extra payments early on have an outsized effect, and when mortgage insurance may come off.
What amortization means
An amortizing loan is repaid in regular installments that cover both interest and part of the principal. With a standard fixed-rate mortgage, the total principal-and-interest payment stays the same every month. What changes is how that payment is divided. The CFPB explains that at the start of the loan you owe more interest, so more of each payment goes to interest. As the balance falls, less interest accrues and more of each payment goes to principal.
An amortization schedule is a table listing every payment over the life of the loan: how much goes to interest, how much goes to principal, and the balance left afterward. Lenders and servicers use these schedules, and you can create your own with our mortgage amortization calculator.
How each payment is split
Each month the calculation works in three steps:
- Interest for the month = current balance × (annual rate ÷ 12).
- Principal for the month = fixed monthly payment − interest for the month.
- New balance = current balance − principal for the month.
Because interest is charged on the remaining balance, every dollar of principal you repay reduces next month's interest a little. That is why the principal share grows every month. The fixed payment itself comes from the standard formula explained in how mortgage payments are calculated.
A sample amortization schedule
Here are the first six payments on a $300,000, 30-year fixed loan at a hypothetical 6.5% rate. The monthly principal-and-interest payment is $1,896.20. Interest is rounded to the cent each month.
| Payment | Payment amount | Interest | Principal | Remaining balance |
|---|---|---|---|---|
| 1 | $1,896.20 | $1,625.00 | $271.20 | $299,728.80 |
| 2 | $1,896.20 | $1,623.53 | $272.67 | $299,456.13 |
| 3 | $1,896.20 | $1,622.05 | $274.15 | $299,181.98 |
| 4 | $1,896.20 | $1,620.57 | $275.63 | $298,906.35 |
| 5 | $1,896.20 | $1,619.08 | $277.12 | $298,629.23 |
| 6 | $1,896.20 | $1,617.57 | $278.63 | $298,350.60 |
Example: Checking the first payment
Interest for month 1 is $300,000 × (0.065 ÷ 12) = $1,625.00. Subtracting that from the $1,896.20 payment leaves $271.20 for principal, so the balance falls to $299,728.80. Month 2's interest is figured on that slightly lower balance, which is why it drops to $1,623.53.
In the first payment, about 86% of the money goes to interest. Over the first full year, this loan's payments total about $22,754, of which about $19,401 is interest and only about $3,353 reduces the balance.
How the balance changes over the years
The table below shows snapshots from the same schedule. Note how slowly the balance falls in the early years and how quickly it falls near the end.
| After payment | Interest in that payment | Principal in that payment | Remaining balance |
|---|---|---|---|
| 12 (year 1) | $1,608.40 | $287.80 | $296,646.88 |
| 60 (year 5) | $1,523.20 | $373.00 | $280,833.26 |
| 120 (year 10) | $1,380.41 | $515.79 | $254,329.14 |
| 180 (year 15) | $1,182.96 | $713.24 | $217,678.77 |
| 240 (year 20) | $909.91 | $986.29 | $166,997.98 |
| 300 (year 25) | $532.35 | $1,363.85 | $96,915.68 |
Halfway through the term, after 15 years, about $217,679 of the original $300,000 is still owed. On this schedule, the principal portion of the payment doesn't exceed the interest portion until payment 233, which comes in the 20th year. The exact crossover point depends on the rate: lower rates reach it sooner, and higher rates reach it later.
This matters if you plan to sell or refinance within a few years. Early on, most of what you have paid has gone to interest, so your equity comes mainly from your down payment and any change in the home's value. If you are weighing a refinance, our refinance break-even calculator can help you compare closing costs with monthly savings. Keep in mind that refinancing also restarts an amortization schedule.
What extra payments do
Any amount you pay above the scheduled payment that the servicer applies to principal lowers the balance immediately. That reduces every future month's interest. With a fixed-rate loan, the required payment usually stays the same, so the loan is paid off sooner.
Example: An extra $100 per month
On the same hypothetical $300,000, 6.5%, 30-year loan, adding $100 to principal every month from the first payment would pay the loan off in about 312 months (26 years) instead of 360. It would also cut total interest by roughly $61,000. Results depend on when you start, whether the servicer applies the extra money to principal, and your loan's terms.
Before making extra payments, check whether your loan has a prepayment penalty. The CFPB notes that some lenders charge a fee if you pay off all or part of a mortgage early, typically within the first three to five years. Small extra principal payments usually don't trigger it, but confirm with your lender. Also make sure that extra payments fit with your emergency savings and other higher-interest debts.
Amortization and mortgage insurance
If you have a conventional loan with private mortgage insurance (PMI), the amortization schedule helps determine when PMI can end. According to the CFPB:
- You can ask your servicer in writing to cancel PMI when your balance is scheduled to fall to 80% of the home's original value, or earlier if extra payments get you there. Conditions apply: you need a good payment history, no junior liens such as a second mortgage, and you may have to show that the home's value hasn't declined.
- The servicer must automatically end PMI on the date your balance is scheduled to reach 78% of the original value, provided you are current on payments.
- PMI must also end the month after you reach the midpoint of the amortization schedule (after 15 years on a 30-year loan), even if the balance hasn't yet reached 78%.
Example: When the schedule reaches 80% and 78%
Suppose you buy a $375,000 home with 10% down and borrow $337,500 at a hypothetical 6.5% for 30 years. On the original schedule, the balance first falls to 80% of the original value ($300,000) after payment 95, just under 8 years in. It reaches 78% ($292,500) after payment 109, a little over 9 years in. Your servicer's records and your loan's terms determine the actual dates.
When loans do not amortize normally
Not every mortgage follows the standard pattern. The Consumer Handbook on Adjustable-Rate Mortgages describes a few variations:
- Adjustable-rate mortgages recalculate the payment when the rate changes, so the schedule is redrawn at each adjustment. See fixed-rate vs. adjustable-rate mortgages.
- Interest-only loans let you pay only interest for a set period. The balance does not fall during that time, and payments rise afterward.
- Negative amortization occurs when payments are smaller than the interest due. The unpaid interest is added to the balance, so you owe more over time.
Key takeaways
- On a fixed-rate mortgage, the payment stays the same, but the share going to principal grows each month.
- Early payments are mostly interest, so the balance and equity build slowly at first.
- Extra principal payments, especially early ones, can shorten the loan and reduce total interest.
- The amortization schedule affects when PMI can be cancelled or must end on conventional loans.
- Interest-only and negatively amortizing loans work differently and carry added risks.
Build a full payment-by-payment schedule for your own loan and test the effect of extra payments.
Open the mortgage amortization calculatorYou can also estimate a monthly payment with the mortgage payment calculator, browse all mortgage calculators, or read our first-time homebuyer's mortgage checklist.
Sources
- How does paying down a mortgage work? — Consumer Financial Protection Bureau
- When can I remove private mortgage insurance (PMI) from my loan? — Consumer Financial Protection Bureau
- What is a prepayment penalty? — Consumer Financial Protection Bureau
- Consumer Handbook on Adjustable-Rate Mortgages (PDF) — Consumer Financial Protection Bureau (originally prepared by the Federal Reserve Board and the Office of Thrift Supervision)
This article is for general educational purposes only and is not financial, legal, or tax advice. ClearPath Guides is not a lender, mortgage broker, or licensed adviser. Examples use hypothetical numbers, and your servicer's records control your actual loan. Read our full disclaimer.
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