How to use the amortization calculator
- Enter the loan amount, the interest rate (APR) and the term in years. If the term has leftover months, open More options and add them.
- Pick the date of your first payment. Every later payment falls one calendar month after the one before, and the dates drive the yearly table and the final payment date.
- To test extra payments, type an extra monthly amount. Under More options you can add a yearly extra (choose the month), a one-time extra with its date, or switch the payment style to biweekly style.
- Read the monthly payment, the final payment date and the total interest. When you add extras, the page also shows the interest saved and how many payments you skip.
- Use the calendar-year table on the page for the overview. Download the CSV or PDF for every single month.
Formula
Monthly rate r = APR / 12, number of payments n = years x 12 + months
Payment = L x r / (1 - (1 + r)^-n), rounded to the cent
Each month: interest = balance x r, rounded to the cent
Principal paid = payment + extra - interest
New balance = old balance - principal paid
Biweekly style: extra each month = payment / 12, the same as 13 monthly payments a year
At 0% APR the payment is the loan divided by the number of payments. The last payment clears whatever balance remains, so cent rounding never leaves a stray balance. An extra payment can never be larger than what is owed.
Worked examples
The basic schedule: a $300,000 loan at 6.5% for 30 years with the first payment on November 9, 2026 has a payment of $1,896.20. In month 1, interest is $300,000 x 0.065 / 12 = $1,625.00, so $271.20 reduces the balance to $299,728.80. All 360 payments end on October 9, 2056 and total interest is $382,636.71.
Reading the calendar-year table: 2026 shows only two payments (November and December), which is $3,792.40, of which $543.87 is principal and $3,248.53 is interest, leaving a balance of $299,456.13. The year 2027 has twelve payments totaling $22,754.40.
An extra $200 each month: the loan ends after 277 payments, on November 9, 2049, which is 83 payments sooner. Total interest falls to $279,186.52, which saves $103,450.19.
Several extras together: $100 a month, plus $5,000 every December, plus a one-time $10,000 in March 2027, ends the loan after 194 payments on December 9, 2042. Interest is $177,511.20, so you save $205,125.51, and you pay $109,648.40 of extra principal along the way.
Biweekly style: adding one-twelfth of the payment, $158.02, to each month ends the loan after 290 payments on December 9, 2050 and saves $87,259.03 of interest.
What an amortization schedule tells you
An amortization schedule lists every payment on a loan and splits it into interest and principal. Interest is charged on the balance you still owe, so it is largest in the first payments. On the example loan, the first 12 payments total $22,754.40, and $19,401.28 of that is interest. Only $3,353.12 reduces the balance. The mix turns around slowly, and the final payments are almost all principal.
That pattern explains why a loan balance seems to barely move in the early years, and why extra principal early in the loan has the largest effect. Each dollar of principal you remove stops accruing interest for every remaining month.
How the three kinds of extra payment differ
An extra monthly payment adds the same amount to principal with every regular payment. A yearly extra is paid only in the month you choose, such as a bonus in December or a tax refund in spring. A one-time extra is applied once, with the payment due in the month of the date you enter, and it is ignored if the loan is already paid off by then.
All three are applied in full to principal in the month they are paid. If a payment would be larger than what is owed, the schedule stops at the exact remaining balance plus that month's interest.
What the biweekly style means here
Paying half of the monthly payment every two weeks produces 26 half payments, which equals 13 full payments a year. This calculator models that result in a simple, checkable way: it adds one-twelfth of the monthly payment to each monthly payment. Real biweekly programs differ in when the money is applied, so confirm with your servicer how it handles biweekly payments before you rely on the savings shown.
How this differs from the mortgage and loan calculators
The mortgage calculator adds property tax, insurance, HOA dues and PMI to a monthly total, and the loan calculator gives a quick payment for any fixed-rate loan. This page is built for the schedule itself: calendar-year totals tied to real dates, three kinds of extra payments, a payoff date and a month-by-month export. If you already own the home and want to plan the payoff from today, the mortgage payoff calculator starts from your current balance instead.
Assumptions and limits
- A fixed-rate, fully amortizing loan with equal monthly payments, each due one calendar month after the previous one.
- Interest each month is the balance times APR / 12, rounded to the nearest cent. A lender that accrues interest daily, or counts days differently, can differ by small amounts.
- Extra payments go entirely to principal in the month they are paid. Check that your servicer applies extra money to principal and not to a future due date.
- Biweekly style is an approximation: one-twelfth of the payment is added each month. It is not a model of any servicer's biweekly program.
- Not modeled: property tax, insurance, PMI, escrow changes, fees, rate changes, skipped or late payments and prepayment penalties.
- This is an estimate for planning. Your loan documents and servicer statements control.
Frequently asked questions
What is amortization?
Amortization is paying off a loan in scheduled installments so that each payment covers the interest due and reduces the principal. By the last payment the balance is zero. The schedule shows the split for every payment.
Why does the 2026 row show only two payments?
The yearly table follows the payment dates. With a first payment on November 9, 2026 only November and December fall in 2026, so that row is $3,792.40 (two payments of $1,896.20). The last year can also be partial.
Does an extra payment really go to principal?
Here it does, by design. In practice servicers may apply extra money to the next due payment unless you mark it as extra principal. Check your statement after the first extra payment to confirm the balance dropped by the full amount.
How is a one-time extra payment dated?
It is added to the payment due in the same calendar month and year as the date you enter. A date before the month of your first payment is rejected, and a date after the loan is paid off is reported as unused.
What do the CSV and PDF contain?
Both list every month with the total payment, principal, interest, the extra part of the payment and the remaining balance. The CSV opens in a spreadsheet. The PDF adds your inputs, the summary and the yearly table.
Can the term be shorter than a year?
Yes. Enter 0 years and a number of months under More options, or mix them, such as 1 year and 6 months for 18 payments. The term can be at most 50 years.