Amortization calculator

An amortization schedule splits each payment on a fixed-rate installment loan into its parts, month by month:

• Interest: the balance at the start of the month × the monthly rate (annual rate / 12).
• Principal: the rest of the payment, which reduces what you owe.
• Balance: what is left after the payment.

The payment stays the same every month, but the mix changes. Early on most of it is interest; by the end it is almost all principal. The schedule shows exactly when the balance drops below a given amount, which is useful if you plan to sell, refinance, or drop PMI on a mortgage.

The payment itself comes from the standard formula M = P × r × (1 + r)^n / ((1 + r)^n − 1), where P is the loan amount, r the monthly rate and n the number of payments.

A personal loan of $25,000 at 12% APR over 60 months.

1. Monthly rate: 12% / 12 = 1%.
2. Payment: 25,000 × 0.01 × 1.01^60 / (1.01^60 − 1) = $556.11.
3. Month 1: interest $250.00, principal $306.11, balance $24,693.89.
4. Month 12: interest $214.59, principal $341.52, balance $21,117.74.
5. Total interest over the loan: $8,366.67.

In the first year you pay $2,791.08 in interest and only $3,882.26 of principal, so after twelve payments you still owe about 84% of the original amount.

Add $100 to every payment and put it toward principal:

• The loan is paid off in 49 months instead of 60, 11 months sooner.
• Total interest falls to $6,631.52, saving $1,735.15.

The chart then shows two lines: dashed for the original schedule and solid with extra payments. You can also add a yearly extra payment (say, from a tax refund or bonus) or a single lump sum in a specific month, and see the effect of biweekly payments.

Tell your lender that extra amounts should go to principal, and check that your loan has no prepayment penalty. The calculator assumes the payment stays the same and the term gets shorter, which is how most US lenders handle extra payments unless you ask for a recast.

A $300,000 mortgage at 6.75% for 30 years:

• Principal and interest: $1,945.79 a month.
• Month 1: $1,687.50 interest and just $258.29 principal.
• Total interest over 30 years: about $400,486, more than the amount borrowed.

With $250 extra each month, the loan ends in 261 months (about 21 years and 9 months) instead of 360, and total interest drops to about $272,801, a saving of roughly $127,685. For taxes, insurance, PMI and HOA dues, use the mortgage calculator, which adds them to the monthly payment.

Download the full schedule as a CSV file with one click. It opens in Excel, Google Sheets, Numbers or LibreOffice, and you can sort, filter or chart it there. The Print button opens a clean page with just the table, which you can print or save as a PDF from your browser.

The schedule can be shown monthly or as a yearly summary that adds up interest, principal and extra payments for each year. Both are free; nothing you enter is sent to a server.

• Each row is rounded to the cent and the final payment is adjusted to clear the remaining balance, so it is usually slightly smaller.
• Some lenders calculate interest daily (actual days / 365), which makes month-to-month interest vary by a few cents or dollars.
• The schedule assumes a fixed rate. For an adjustable-rate loan, the payment changes after each adjustment; try a higher rate to see what your budget could handle.
• The APR on your Loan Estimate or credit agreement includes fees that this schedule doesn't. Use it to compare lenders.

This is an estimate for planning, not financial advice or a loan offer. Your lender's schedule is the one that counts.