What Is Amortization?
Amortization is paying off a loan through regular payments that cover each month's interest and part of the principal, so the balance reaches zero by the end of the term. It matters because early payments are mostly interest, which shapes how fast you build equity and what prepaying or refinancing saves.
Amortization in plain English
Amortization is how a loan gets paid down over time. Each fixed monthly payment covers that month's interest first; whatever is left reduces the balance.
Because interest is charged on the remaining balance, early payments are mostly interest and later payments are mostly principal.
Formula
Monthly Payment = Loan × r ÷ [1 − (1 + r)^−n]- Loan
- The amount borrowed.
- r
- The monthly interest rate: the annual rate ÷ 12 (6.5% a year is 0.005417 a month).
- n
- The number of monthly payments (360 for 30 years).
Related forms: Interest This Month = Remaining Balance × r; Principal This Month = Monthly Payment − Interest This Month.
Worked example
How a 30-year payment splits over time
Illustrative example - round numbers, not current market data. Calculated with Reaixo's calculator engines.
Assumptions
- Loan
- $300,000 at 6.5%, 30-year fixed
| Step | Calculation | Result |
|---|---|---|
| 1. Monthly principal and interest | $300,000 at 6.5% over 360 months | $1,896.20 |
| 2. Month 1 interest | $300,000 × 6.5% ÷ 12 | $1,625.00 |
| 3. Month 1 principal | $1,896.20 − $1,625.00 | $271.20 |
| 4. Paid in the first 5 years | $1,896.20 × 60 | $113,772 |
| 5. Principal repaid in those 5 years | $300,000 − $280,833 balance | $19,167 |
Share of the first 5 years that is principal: 17%. Of the $113,772 paid in the first five years, only $19,167 reduces the balance. Early payments are mostly interest, which is why equity from payments builds slowly at first and quickly near the end.
What this calculation leaves out
- Fixed-rate, fully amortizing loan; taxes, insurance and mortgage insurance are not part of the schedule.
- Extra principal payments shorten the schedule and cut total interest.
Try it: Amortization with your own numbers
Interactive and illustrative: change any value and the results update instantly in your browser. The figures come from the same engines as REAIXO's full calculators.
Amortization: where each payment goes
The payment stays the same, but early payments are mostly interest. Each year a little more goes to principal.
- Monthly principal & interest
- $1,896
- Total interest over the term
- $382,633
- Principal overtakes interest
- Year 20
- Principal
- Interest
Show the numbers as a table
| Year | Principal paid | Interest paid | Balance at year end |
|---|---|---|---|
| 1 | $3,353 | $19,401 | $296,647 |
| 2 | $3,578 | $19,177 | $293,069 |
| 3 | $3,817 | $18,937 | $289,252 |
| 4 | $4,073 | $18,681 | $285,179 |
| 5 | $4,346 | $18,409 | $280,833 |
| 6 | $4,637 | $18,118 | $276,196 |
| 7 | $4,947 | $17,807 | $271,249 |
| 8 | $5,279 | $17,476 | $265,970 |
| 9 | $5,632 | $17,122 | $260,338 |
| 10 | $6,009 | $16,745 | $254,328 |
| 11 | $6,412 | $16,343 | $247,916 |
| 12 | $6,841 | $15,913 | $241,075 |
| 13 | $7,299 | $15,455 | $233,776 |
| 14 | $7,788 | $14,966 | $225,987 |
| 15 | $8,310 | $14,445 | $217,677 |
| 16 | $8,866 | $13,888 | $208,811 |
| 17 | $9,460 | $13,294 | $199,351 |
| 18 | $10,094 | $12,661 | $189,257 |
| 19 | $10,770 | $11,985 | $178,487 |
| 20 | $11,491 | $11,263 | $166,996 |
| 21 | $12,261 | $10,494 | $154,735 |
| 22 | $13,082 | $9,673 | $141,653 |
| 23 | $13,958 | $8,797 | $127,695 |
| 24 | $14,893 | $7,862 | $112,803 |
| 25 | $15,890 | $6,864 | $96,912 |
| 26 | $16,954 | $5,800 | $79,958 |
| 27 | $18,090 | $4,665 | $61,868 |
| 28 | $19,301 | $3,453 | $42,567 |
| 29 | $20,594 | $2,161 | $21,973 |
| 30 | $21,973 | $781 | $0 |
Formula
Payment = Loan × r ÷ (1 − (1 + r)^−n)Interest this month = Balance × r; Principal = Payment − InterestAssumptions
- Fixed rate, no extra payments, no escrow.
- Totals are the sum of scheduled monthly payments, rounded to the cent.
Why it matters
Amortization explains why selling or refinancing in the first few years leaves you with little equity from payments, and why extra principal payments early in the loan save the most interest.
What it means for you
How does it affect my budget?
Amortization does not change your monthly principal and interest on a fixed-rate loan; it changes how fast you build equity.
Common mistakes
- Assuming half of each early payment goes to principal.
- Restarting a 30-year schedule with each refinance without counting the extra years of interest.
Interest-Only Loan vs. Fully-Amortizing Loan
Payments cover interest only for an initial period — lower payments up front, but no equity built through payments and a payment jump when the period ends.
Every payment includes both principal and interest from day one, steadily paying the loan down to zero by the end of the term.
Amortization: frequently asked questions
Why is most of my early mortgage payment interest?
Interest is calculated on the remaining balance, which is largest at the start. As the balance falls, the interest portion shrinks and more of the same payment goes to principal.
Do extra payments shorten amortization?
Yes. Extra principal lowers the balance, so future interest is smaller and the loan is paid off sooner - provided the servicer applies the money to principal.
What is negative amortization?
It happens when payments are smaller than the interest due, so the unpaid interest is added to the balance and the loan grows instead of shrinking.
Related Terms
More Financing Terms
Recommended next step
See the full amortization schedule for your loan.
Mortgage payment calculator →Sources and review
- How does paying down a mortgage work?, Consumer Financial Protection Bureau. Supports: Each payment covers interest and principal, with the share of principal increasing over time.
Where this applies: Applies to standard fully amortizing loans everywhere; the example is a U.S. 30-year fixed-rate mortgage.
Last reviewed: · Updated:
Examples use illustrative figures; rules of thumb are labelled as such. Rates, limits and program rules change - confirm current figures with your lender or a qualified professional.
This definition is provided for general educational purposes and is not financial, legal, tax, or real estate advice. Verify important decisions with appropriately qualified professionals.
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