Amortization Calculator
Generate a full loan amortization schedule — monthly payment, total interest, payoff date, and extra-payment savings, instantly
What Is an Amortization Calculator?
An amortization calculator instantly generates the complete payment schedule for a fixed-rate loan, showing exactly how much of every single payment goes toward interest versus principal, and how your remaining balance shrinks over time. Instead of manually working through dozens or hundreds of payment calculations, this tool does it in a fraction of a second — for mortgages, auto loans, personal loans, student loans, or any other fixed-payment loan.
How to Use This Amortization Calculator
- Enter your loan amount, annual interest rate, and loan term (in years or months).
- Optionally set a start date and any extra monthly or one-time payments in Advanced Options.
- Click Calculate to instantly see your monthly payment, total interest, and payoff date.
- Review the full amortization schedule in Yearly or Monthly view, and the Principal vs. Interest and Balance Over Time charts.
- Use Copy, Print, or Share to save or send your results.
The Amortization Formula
Every fixed-rate, fully-amortizing loan uses the same core formula to determine the level monthly payment:
M = P × [r(1+r)n] / [(1+r)n − 1]
Where M is the monthly payment, P is the loan principal (amount borrowed), r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (term in months).
How an Amortization Schedule Is Built, Month by Month
- Calculate this period's interest: current balance × monthly interest rate.
- Subtract that interest from the fixed payment to get the principal portion.
- Subtract the principal portion from the current balance to get the new balance.
- Repeat for every remaining payment until the balance reaches zero.
This calculator repeats that exact process automatically, month by month, and rolls the results up into both a monthly and yearly view.
Explanation of Every Input
Loan Amount
The total amount being borrowed (or still owed, if you're modeling an existing loan) at the start of the schedule.
Annual Interest Rate
The yearly interest rate quoted by your lender. This is automatically divided by 12 to get the monthly rate used in each period's calculation.
Loan Term
How long you have to repay the loan, entered in years or months — common terms range from 1-2 years for personal loans up to 30 years for mortgages.
Start Date (Optional)
Sets the calendar date of your first payment so the schedule shows real dates instead of just "Month 1, Month 2," etc.
Extra Monthly & One-Time Payments (Optional)
Model paying more than the required minimum — either every month or as a single lump sum in a specific month — to see exactly how much time and interest that saves.
Why Interest Is "Front-Loaded" in Every Amortization Schedule
Because interest for each period is calculated on the current balance, and the balance is highest at the very start of the loan, early payments are mostly interest with only a small amount of principal. As the balance drops with each payment, the interest portion shrinks and the principal portion grows — by the final payments, almost the entire amount goes toward principal. This is normal, expected behavior for every standard amortizing loan, not a sign of a bad deal.
The Power of Extra Payments
Because interest is always calculated on the outstanding balance, any extra amount applied to principal stops accruing interest immediately and for the rest of the loan's life — this compounding effect means even small, consistent extra payments can meaningfully shorten a long-term loan and reduce total interest paid, which this calculator quantifies precisely using the Extra Monthly Payment and One-Time Extra Payment fields.
Advantages of Using This Amortization Calculator
- Works for any fixed-rate loan type — mortgage, auto, personal, or student loans.
- Full monthly AND yearly schedule views, not just a single summary number.
- Models extra monthly and one-time payments to quantify real savings.
- Visualizes the principal/interest split and balance decline with built-in charts.
- 100% free, runs instantly in your browser, no sign-up required.
Limitations
- Assumes a fixed interest rate for the entire term (not adjustable-rate).
- Assumes standard monthly payments (no bi-weekly/weekly schedule modeling yet).
- Does not include taxes, insurance, or other loan-specific fees — see our Mortgage or Auto Loan calculators for those.
Common Amortization Mistakes to Avoid
- Assuming your loan balance drops evenly each month — it doesn't, due to front-loaded interest.
- Ignoring how much a longer term increases total interest, even at a lower rate.
- Forgetting that even small extra payments compound in your favor over time.
- Comparing two loans by monthly payment alone instead of total interest paid.
Worked Examples
Personal Loan, 5-Year Term
Loan Amount: $15,000
Interest Rate: 9%
Term: 5 years (60 months)
Monthly Payment: $311.38
Total Paid: $18,682.80
Total Interest: $3,682.80
A shorter-term personal loan keeps total interest relatively low even at a higher interest rate, because the balance is paid down quickly.
Same Loan with $50 Extra Monthly
Loan Amount: $15,000
Interest Rate: 9%
Term: 5 years (60 months)
Monthly Payment: $311.38 + $50 extra
Total Paid: $17,932 (approx.)
Total Interest: $2,932 (approx.)
A modest $50/month extra payment on this loan pays it off roughly 8-9 months early and saves around $750 in interest.
30-Year Mortgage-Style Loan
Loan Amount: $300,000
Interest Rate: 6.5%
Term: 30 years (360 months)
Monthly Payment: $1,896.20
Total Paid: $682,632
Total Interest: $382,632
Over a 30-year amortization, total interest can exceed the original loan amount — a stark illustration of how much time affects total cost.
15-Year Version (Same Loan)
Loan Amount: $300,000
Interest Rate: 6.5%
Term: 15 years (180 months)
Monthly Payment: $2,613.32
Total Paid: $470,398
Total Interest: $170,398
Cutting the term in half more than doubles the monthly payment but reduces total interest by well over $200,000 compared to the 30-year version.
Frequently Asked Questions About Amortization
What is loan amortization?
Amortization is the process of paying off a loan through regular, fixed payments over time, where each payment is split between interest (the cost of borrowing) and principal (the amount that reduces your balance). An amortization schedule lists every payment across the life of the loan, showing exactly how that split changes month by month.
How do I calculate an amortization schedule?
For each payment period, interest is calculated on the current balance (balance × monthly rate), the remainder of the fixed payment goes to principal, and the new balance is the old balance minus that principal amount. This calculator repeats that process automatically for every payment and lists the results in the schedule below.
Why is more of my early payments going to interest?
Interest is calculated on your current balance, which is largest at the very start of the loan, so early payments are interest-heavy. As the balance shrinks with each payment, less interest accrues and progressively more of each payment goes toward principal — this pattern is the defining feature of an amortizing loan.
What is the amortization formula used here?
This calculator uses the standard fixed-payment amortization formula: M = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1], where M is the monthly payment, P is the loan amount, r is the monthly interest rate, and n is the total number of payments.
How much can extra payments save on an amortizing loan?
Every extra dollar applied to principal stops accruing interest immediately, which compounds over the life of the loan — even modest recurring extra payments can shave years off a long-term loan and save a substantial amount in total interest, shown directly in this calculator's results.
What is negative amortization?
Negative amortization happens when a payment is smaller than the interest accrued for that period, causing the unpaid interest to be added to the balance instead of reducing it — meaning the loan balance actually grows over time. This calculator always assumes a standard fully-amortizing payment, which avoids this scenario.
Does a lower interest rate always mean a shorter amortization schedule?
Not necessarily — the interest rate affects how much of each payment goes to interest versus principal, but the schedule length depends on the loan term you choose. A lower rate does reduce total interest paid and can let you pay off faster if you keep payments the same while the rate drops.
What is the difference between amortization and depreciation?
Amortization refers to paying down a loan balance over time through scheduled payments, while depreciation refers to an asset (like a car or piece of equipment) losing value over time — the two are related in personal finance but describe fundamentally different processes.
Can this calculator handle bi-weekly or accelerated payments?
This version focuses on standard monthly amortization with optional extra monthly and one-time payments, which can approximate the effect of an accelerated payoff strategy — a dedicated bi-weekly payment mode may be added in a future update.
Why does my payoff date move up when I add extra payments?
Extra payments reduce the principal balance faster than scheduled, which means less interest accrues going forward and the loan reaches a zero balance in fewer total payments — the calculator recalculates the exact payoff date based on your extra payment inputs.
Is loan interest tax-deductible?
It depends on the loan type and your local tax rules — mortgage interest is deductible under certain conditions in some countries, while most personal and auto loan interest generally is not. Consult a tax professional for guidance specific to your situation.
How does refinancing affect my amortization schedule?
Refinancing replaces your current loan with a new one (often at a different rate or term), which resets the amortization schedule from the new loan's starting balance — run the new loan's numbers through this calculator to compare against your current schedule.
What loan types can I use this calculator for?
This calculator works for any fixed-rate, fully-amortizing loan — mortgages, auto loans, personal loans, and student loans all follow the same underlying math, so you can use it for any of them by entering the relevant amount, rate, and term.
Why does the total interest change so much with a longer term?
A longer term lowers the monthly payment but keeps a higher balance outstanding for more months, so interest — which is calculated on the remaining balance — accrues for a longer period, often resulting in significantly more total interest paid over the life of the loan.
Conclusion
Understanding your amortization schedule turns an abstract loan into a concrete, month-by-month plan — you can see exactly when you'll be debt-free, how much interest you'll pay in total, and precisely how much extra payments would save you. Use this calculator any time you're taking out a new loan, considering refinancing, or just want to see the real cost of debt you already have.