Amortization Calculator

Planning a boat purchase? The boat loan calculator separates price, down payment, financed or upfront purchase costs and an annual boating reserve from the loan payment.

For an installment loan with a quoted origination fee or monthly insurance, use the personal loan calculator to separate disbursement, net cash available and modeled borrowing costs.

Loan amortization schedule

An amortization schedule separates every payment into interest and principal. Interest is calculated from the opening balance, so early payments generally contain more interest. As principal falls, less interest accrues and more of the same scheduled payment reduces the balance. The CFPB explains how a fixed-rate mortgage amortizes; taxes and insurance are separate from principal and interest.

monthly payment = P x r x (1 + r)^n / ((1 + r)^n - 1)

Here, P is the loan amount, r is the monthly interest rate, and n is the number of monthly payments. At a zero rate, payment equals principal divided by the number of months.

Amortization example

A $200,000 fixed-rate loan at 6% for 15 years has a scheduled monthly payment of about $1,687.71. Without fees or extra payments, 180 payments total about $303,788 and include about $103,788 of interest.

Amortization calculator with extra payments

Enable extra payments to choose when monthly and yearly extras start, plus one main and up to ten additional dated one-time payments. Monthly extras repeat from the selected month; yearly extras repeat every twelve months from their own selected month. Amounts due in the same month add together. Each scheduled payment pays the month's interest first; extras then reduce principal for later months. This does not recast the scheduled payment.

For the $200,000 example, use October 2026 as the first payment month and add $100 monthly starting November 2026. The model finishes in 165 payments, in June 2040, with about $93,886.58 interest and $9,901.88 interest saved. Actual extra principal is $16,300: the first month has no extra, and the final partial payment clears the balance without the full requested extra.

Regular payments versus total paid

In that extra-payment example, regular payment portions total $277,586.58 and extra principal totals $16,300. Together they are $293,886.58, equal to the original $200,000 principal plus $93,886.58 interest. Extra principal is part of repaying the original debt, not an additional borrowing charge. The principal-and-interest pie includes all principal once and all interest once; it does not count extras again as another slice.

Interest rate versus APR

This model treats the entered percentage as a fixed nominal annual rate divided by 12. It does not separately add origination fees, points, closing costs, insurance, or taxes. The Consumer Financial Protection Bureau explains that APR can include the interest rate plus certain lender fees. Use the rate that matches the schedule you want to model.

Payment months, rounding and limits

The first payment month labels row 1, and the payoff date is the month of the final row. Annual rows group twelve loan payments, not calendar tax years. Positive extras must be dated between the first and original final payment months. Extras scheduled after an earlier modeled payoff are not charged and are identified in the results. Turning extras off excludes those amounts while preserving the entries for reuse.

Loan principal is $0.01-$1 billion, the fixed annual note rate is 0%-100%, and the term is 1-1200 whole months. Years and additional months must be whole numbers; additional months are 0-11. Each extra amount is $0-$1 billion. Blank optional extra amounts mean none; the loan amount, rate, term and first payment month remain required. Date labels must fit years 0001-9999. These numerical limits do not imply that a lender offers such terms.

Calculations retain full precision before display rounding, so adding already-rounded rows can differ from the displayed total. The final payment clears the actual remaining principal and any excess requested extra is not charged. The schedule assumes equal monthly periods, a fixed rate and no missed payments. It excludes origination fees, taxes, insurance, daily interest, payment-date irregularities, prepayment penalties and recasting. Follow your lender's principal-only instructions and compare with its own payoff statement.

Related loan tools

Use the mortgage calculator when property tax and insurance matter, the payment calculator to solve for either payment or payoff term, and the loan calculator for custom compounding or repayment frequencies.

Frequently asked questions

What is the difference between principal and interest?

Principal is the amount borrowed or still owed. Interest is the borrowing charge calculated from the outstanding balance.

Do extra payments always save interest?

They generally save interest on a fixed-rate amortizing loan when the lender applies them promptly to principal and no offsetting fee applies.

Why can my lender's schedule differ?

Lenders may use exact payment dates, daily interest, contractual rounding, escrow, fees, or principal-payment processing rules that this monthly planning model does not include.