Amortization Calculator

What This Calculator Does

An amortization calculator shows you the full repayment plan for a fixed-rate loan. It breaks down each payment into the portion that goes toward interest and the portion that reduces your principal balance. The result is a complete schedule that shows how your loan balance declines over time until it reaches zero.

This is useful for mortgages, auto loans, personal loans, and any other installment loan with a fixed interest rate and fixed monthly payment.

How Amortization Works

With a standard amortizing loan, your monthly payment stays the same for the entire term. However, the split between interest and principal changes with every payment.

Early in the schedule, a larger portion of your payment goes toward interest because the outstanding balance is highest. As you pay down the principal, the interest portion decreases, and more of your payment goes toward reducing the balance. This process accelerates over time, which is why the principal balance drops faster in the later years of the loan.

The calculator uses the standard amortization formula to determine your fixed monthly payment based on three inputs:

• Loan amount – the total amount you borrow
• Interest rate – the annual percentage rate (APR) on the loan
• Loan term – the total repayment period in years or months

How to Use the Calculator

Enter your loan amount, interest rate, and loan term. The calculator will instantly generate your monthly payment and a full amortization schedule.

The schedule shows each payment period with:

• Payment number
• Total payment amount
• Interest paid in that period
• Principal paid in that period
• Remaining balance after the payment

You can adjust any input to see how changes affect your payment and total interest cost. This is helpful for comparing different loan scenarios before committing to a lender.

Example Scenario

Consider a $300,000 mortgage at a 6.5% annual interest rate with a 30-year term.

The monthly payment would be approximately $1,896. Over the life of the loan, you would pay roughly $382,000 in total interest. The first payment would include about $1,625 in interest and only $271 toward principal. By the final year, nearly the entire payment goes toward principal.

If you increased the monthly payment by $200, you would save tens of thousands in interest and pay off the loan several years earlier. The calculator lets you test these scenarios directly.

Understanding Your Results

The amortization schedule provides a complete picture of your loan over time. Key figures to pay attention to:

• Monthly payment – your fixed payment for the entire term
• Total interest paid – the cumulative cost of borrowing
• Total cost of the loan – principal plus all interest
• Payoff date – when the loan will be fully repaid

The schedule also shows you the exact point where your principal balance crosses below half of the original loan amount, which is a useful milestone for tracking progress.

Common Mistakes to Avoid

• Using the wrong interest rate – Make sure you enter the annual rate, not a monthly rate. The calculator handles the conversion automatically.
• Confusing term length – A 30-year mortgage has 360 monthly payments. Double-check that your term matches the payment frequency.
• Ignoring additional costs – This calculator covers principal and interest only. Property taxes, insurance, and PMI are separate costs not included here.
• Assuming the schedule is fixed – The schedule assumes you make every payment on time and never prepay. Any extra payments will change the schedule.

Limitations

This calculator assumes a fixed interest rate for the entire loan term. It does not account for adjustable-rate mortgages (ARMs), interest-only loans, or balloon payments. It also does not include fees, closing costs, or escrow amounts.

The results are estimates based on standard amortization formulas. Actual loan terms may vary based on lender policies, compounding frequency, and payment timing.

Practical Use Cases

• Mortgage planning – Compare 15-year vs. 30-year terms to see how a shorter term affects monthly payment and total interest.
• Auto loan evaluation – Test different down payments and interest rates to find a payment that fits your budget.
• Refinancing analysis – Compare your current loan schedule against a new loan with a lower rate or shorter term.
• Extra payment planning – See how making additional principal payments reduces total interest and shortens the loan term.