Amortization Calculator
Use this free amortization calculator to see exactly how a fixed-rate loan gets paid off over time. Enter your loan amount, interest rate, and loan term to instantly calculate your monthly payment, total interest cost, and a full amortization schedule showing how much of every payment goes toward principal versus interest. Add an optional extra monthly payment to see how much faster you could be debt-free and how much interest you'd save.
What Is an Amortization Calculator?
An amortization calculator shows how a fixed-rate loan — such as a mortgage, auto loan, personal loan, or student loan — is paid off through equal periodic payments over time. Each payment covers both interest on the outstanding balance and a portion of the principal, and this calculator breaks down exactly how that split changes from your first payment to your last. It also produces a complete amortization schedule so you can see your remaining balance, cumulative interest, and cumulative principal at any point during the loan.
How an Amortization Schedule Is Calculated
Every amortized loan uses the same fixed-payment formula to determine the monthly payment amount:
M = P × [r(1+r)n] ÷ [(1+r)n − 1]
Where M is the fixed monthly payment, P is the original loan principal, r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments. Once the payment is known, each period's interest charge is calculated by multiplying the remaining balance by the monthly rate; the rest of the payment reduces the principal, and the process repeats until the balance reaches zero.
Why Early Payments Are Mostly Interest
Interest is always calculated on the current outstanding balance, which is largest at the very start of the loan. That means early payments are weighted heavily toward interest, with only a small amount reducing principal. As the balance gradually shrinks, less interest accrues each period, so a growing share of every fixed payment goes toward principal — a pattern that accelerates noticeably in the second half of the loan term.
Loan Term: Monthly Payment vs. Total Interest
| Loan Term | Monthly Payment | Total Interest Paid | Best For |
|---|---|---|---|
| Shorter (e.g. 15 years) | Higher | Lower | Borrowers who can afford larger payments and want to minimize total cost |
| Longer (e.g. 30 years) | Lower | Higher | Borrowers who prioritize lower monthly cash outflow and flexibility |
A shorter term means larger monthly payments but a much smaller total interest bill, because the balance is paid down faster and less time is spent accruing interest. A longer term spreads payments out and lowers the monthly amount, but the loan accrues interest for more periods, which increases the total cost of borrowing. Adjust the loan term field above to compare both scenarios directly.
The Impact of Extra Principal Payments
Any extra amount paid beyond the required monthly payment is applied directly to the principal balance, which lowers the base on which future interest is calculated. Because interest compounds on a smaller balance from that point forward, even modest extra payments can meaningfully shorten the loan term and reduce total interest paid. Use the "Extra Monthly Payment" field above to see how much time and interest a consistent extra payment could save you.
Amortization vs. Depreciation
Amortization and depreciation both spread a cost over time, but they apply to different things. Amortization refers to paying down a loan balance in fixed installments, or to spreading the cost of an intangible asset — such as a patent or a loan's closing costs — over its useful life. Depreciation specifically refers to spreading the cost of a tangible physical asset, like a vehicle or equipment, over its useful life. This calculator focuses on loan amortization.
Which Loans Are Amortized?
Most fixed-rate installment loans follow an amortization schedule, including mortgages, auto loans, personal loans, and federal or private student loans. Adjustable-rate loans are also amortized, though the payment can change when the rate resets. Revolving credit — such as credit cards and lines of credit — does not follow a fixed amortization schedule, since the balance and required payment fluctuate with usage.
Strategies to Pay Off a Loan Faster
- Make consistent extra principal payments, even a small fixed amount each month.
- Switch to biweekly payments, which results in one extra full payment per year.
- Apply lump sums — bonuses, tax refunds, or gifts — directly to the principal balance.
- Refinance to a shorter term if your budget and interest rate environment allow it.
- Round payments up to the nearest convenient amount to steadily chip away at principal.
Common Amortization Mistakes to Avoid
- Not confirming extra payments go to principal. Some lenders apply extra amounts to future interest by default unless you specify otherwise.
- Underestimating total interest cost. On a long-term loan, total interest paid can approach or exceed the original loan amount.
- Ignoring the effect of refinancing on the schedule. Refinancing restarts amortization, which can mean paying more interest again in the early years even at a lower rate.
- Comparing loans by monthly payment alone. A lower payment from a longer term often means significantly more interest paid overall.
- Forgetting other loan costs. Origination fees, closing costs, and insurance are not part of the amortization formula but still affect the true cost of borrowing.
Frequently Asked Questions
Q: What is loan amortization?
A: Loan amortization is the process of paying off a loan through fixed, regular payments where each payment is split between interest and principal, with the interest portion shrinking and the principal portion growing over the life of the loan.
Q: How do you calculate an amortization schedule?
A: An amortization schedule is calculated by applying the periodic interest rate to the remaining loan balance each period to find the interest portion of the payment, then subtracting that from the fixed payment to find the principal portion, and reducing the balance accordingly until it reaches zero.
Q: Why do you pay more interest at the beginning of a loan?
A: Interest is calculated on the outstanding balance, which is highest at the start of the loan, so early payments contain a larger interest portion. As the balance shrinks with each payment, less interest accrues and more of each payment goes toward principal.
Q: How does making extra payments affect amortization?
A: Extra payments applied directly to principal reduce the outstanding balance faster, which lowers the interest charged in every subsequent period, shortens the loan term, and reduces the total interest paid over the life of the loan.
Q: What is the difference between amortization and depreciation?
A: Amortization refers to paying down a loan balance over time or spreading the cost of an intangible asset over its useful life, while depreciation refers specifically to spreading the cost of a tangible physical asset over its useful life.
Q: Is a longer loan term always worse?
A: A longer loan term lowers the monthly payment but increases the total interest paid over the life of the loan because the balance stays higher for longer. A shorter term raises the monthly payment but reduces total interest paid.
Q: What loans use amortization schedules?
A: Most fixed-rate installment loans use amortization schedules, including mortgages, auto loans, personal loans, and student loans. Credit cards and other revolving credit lines do not follow a fixed amortization schedule.
Q: How can I pay off my loan faster?
A: Common strategies include making extra principal payments, switching to biweekly payments instead of monthly, refinancing to a shorter term, and applying any lump sums such as bonuses or tax refunds directly to the principal balance.
This calculator provides estimates for informational purposes only and does not constitute financial or lending advice. Actual payments, fees, and terms depend on your lender's contract. Consult a licensed financial professional for guidance specific to your situation.