Amortization Calculator

Direct answer

Enter the amount borrowed, annual note interest rate, term, payment frequency, and start date. The calculator returns the scheduled payment, total interest, payoff date, and a period-by-period balance. Add a recurring, annual, or one-time extra payment to compare the revised payoff with the baseline.

Continue with the Understand the schedule. Read principal, interest, and balance correctly.

Formula used

For a fixed-rate, fully amortizing loan with equal periodic payments:

M = P × r(1 + r)^n / ((1 + r)^n − 1)

P is starting principal, r is the periodic note rate, n is the number of scheduled payments, and M is the periodic principal-and-interest payment. If r = 0, use M = P / n.

For each period:

1. Interest = opening balance × periodic rate.
2. Scheduled principal = scheduled payment − interest.
3. Extra principal = the applicable recurring, annual, or one-time amount.
4. Closing balance = opening balance − scheduled principal − extra principal.
5. The last payment is reduced so the balance ends at zero instead of becoming negative.

Continue with Understand the schedule or Compare extra-payment strategies for the next calculation.

Note rate, APR, and payment frequency

The note interest rate is the contractual rate used to accrue interest. APR is a broader comparison measure that can include points, broker fees, and other charges. Entering APR as though it were the note rate usually produces the wrong contractual schedule.

For monthly payments, the simplified periodic rate is annual note rate / 12. A true biweekly schedule needs its own defined periodic-rate convention and 26 payment dates. “Accelerated biweekly” commonly means half the monthly payment every two weeks, producing about 13 monthly-payment equivalents per year. Some servicers hold partial payments until a full payment is available, so the calculator must disclose exactly when funds reduce principal.

Worked fixed-rate example

For a $300,000 loan, 6.50% annual note rate, 30-year term, and monthly payments:

• Scheduled principal-and-interest payment: $1,896.20.
• First-payment interest: $1,625.00; first-payment principal: $271.20.
• Balance after payment 120: $254,328.38.
• Total scheduled interest, subject to the stated rounding convention: $382,633.47.

With an extra $200 applied to principal every month under this model:

• Modeled payoff: 277 payments instead of 360.
• Modeled time saved: 83 months.
• Modeled interest saved: $103,448.79.

These values assume the extra amount is accepted and applied to principal on each due date, with no penalty and no recast. Your contract and servicer control the actual result.

To compare this result with another relevant method, open the Debt Payoff Planner. Compare strategies for several debts under one monthly budget.

How to read the schedule

The opening balance is what remains before a payment. Interest is the financing charge for that period. Principal is the portion that reduces the debt. The closing balance becomes the next period's opening balance. On a standard fixed-rate schedule, the payment stays level while the interest share generally falls and the principal share rises.

Use annual summary rows for orientation and expand a year when you need an exact period. The CSV should preserve full dates, payment, scheduled principal, extra principal, interest, and remaining balance so the result can be independently reconciled.

Extra-payment sequence

Show a baseline and an extra-payment scenario side by side. Apply recurring extra principal every eligible payment, annual extra principal in the selected month, and a one-time amount on the selected date. Cap principal so the final balance is zero, reduce the final payment, and report interest saved as baseline interest minus revised interest. Do not call a shorter modeled schedule a lender-approved payoff.

Before sending extra money, confirm that the loan permits it, whether a penalty applies, and how to designate the amount as principal. CFPB notes that small extra-principal payments do not normally trigger a prepayment penalty, but borrowers should check the contract and lender.

Before committing extra cash, compare recurring, annual, and one-time extra-principal strategies.

Escrow and all-in payment

Property tax, homeowners insurance, and HOA amounts can help budget the all-in outflow, but they do not amortize the loan principal. Display escrow separately from principal and interest, and do not include escrow in “total interest” or “loan cost.” Escrow amounts can change even when a fixed-rate principal-and-interest payment does not.

Precision and rounding

Carry sufficient internal precision for rate conversion, interest, and balance. Round displayed currency to cents. Document whether the schedule rounds each period before carrying the balance or carries high precision and rounds only for display; lenders may use different contract-specific methods. Reconcile the sum of principal to the original principal and force only the final payment—not earlier rows—to clear a residual cent.

Limits of this calculator

The standard schedule is suitable for fixed-rate, fully amortizing loans with the stated payment convention. It does not predict future ARM resets, daily simple interest, late fees, skipped payments, payment holidays, interest-only periods, balloon terms, negative amortization, recasts, or contract-specific fees unless those features are explicitly modeled. A payoff amount can include interest through a specified date and unpaid fees, so it can differ from the current principal balance.

For a real settlement date, understand why a projected balance is not a payoff quote.

Common mistakes

• Entering APR instead of the note rate.
• Treating an all-in mortgage payment as principal and interest.
• Assuming biweekly partial payments reduce principal immediately.
• Applying an annual extra payment in the wrong month.
• Counting extra principal as interest or escrow.
• Comparing two schedules with different start dates or rounding rules.
• Calling the displayed balance a payoff quote.
• Using a fixed-rate schedule for an ARM after its initial fixed period.

Inputs, outputs and result meaning

Calculates scheduled principal-and-interest payment, payment plus entered extra and escrow, baseline total interest, and interest with entered extras from amount borrowed, annual interest rate (note rate), loan term, and payment frequency with visible method, validation, precision, and limitations.

Inputs

Amount borrowed

Starting principal, excluding escrow and fees. Supported units include US dollars ($). The supported range is 0.01 through 100,000,000.

Annual interest rate (note rate)

Use the contractual note rate, not APR. Supported units include percent (%). The supported range is 0 through 40.

Loan term

Scheduled repayment term. Supported units include years (yr). The supported range is 0.01 through 50.

Payment frequency

True biweekly uses rate ÷ 26. Accelerated biweekly uses half the monthly payment every 14 days. Available choices are Monthly, True biweekly (26/year), and Accelerated biweekly.

First payment date

Date of the first modeled payment.

Extra principal each payment

Applied with every modeled payment. Supported units include US dollars ($). The supported range is 0 through 10,000,000.

Annual extra principal

Applied once in the selected calendar month. Supported units include US dollars ($). The supported range is 0 through 10,000,000.

Annual extra month

First eligible payment in this month. Available choices are January, February, March, April, May, June, July, and August.

One-time extra principal

Applied on the first modeled payment on or after its selected date. Supported units include US dollars ($). The supported range is 0 through 100,000,000.

One-time extra date

First eligible payment on or after this date.

Monthly tax and insurance escrow

Displayed in the all-in outflow but excluded from principal, interest, and payoff. Supported units include US dollars ($). The supported range is 0 through 1,000,000.

Outputs

Scheduled principal-and-interest payment

This is the primary result. The visible value uses up to 2 decimal places according to the output rule.

Payment plus entered extra and escrow

The visible value uses up to 2 decimal places according to the output rule.

Baseline total interest

The visible value uses up to 2 decimal places according to the output rule.

Interest with entered extras

The visible value uses up to 2 decimal places according to the output rule.

Modeled interest saved

The visible value uses up to 2 decimal places according to the output rule.

Payments with entered extras

It is displayed in payments. The visible value is displayed without decimal places.

Payments saved

It is displayed in payments. The visible value is displayed without decimal places.

First-payment interest

The visible value uses up to 2 decimal places according to the output rule.

First scheduled principal

The visible value uses up to 2 decimal places according to the output rule.

Baseline balance after payment 120

The visible value uses up to 2 decimal places according to the output rule.

M = P × r(1+r)^n ÷ ((1+r)^n−1), with r = annual note rate ÷ 12. Keep the result label, unit, selected mode, and stated limitations together when sharing the answer.

Frequently asked questions

Primary sources

• CFPB — What is amortization?: https://www.consumerfinance.gov/ask-cfpb/what-is-amortization-and-how-could-it-affect-my-auto-loan-en-771/
• CFPB — Interest rate versus APR: https://www.consumerfinance.gov/ask-cfpb/what-is-the-difference-between-a-mortgage-interest-rate-and-an-apr-en-135/
• CFPB — Payoff amount versus current balance: https://www.consumerfinance.gov/ask-cfpb/what-is-a-payoff-amount-and-is-it-the-same-as-my-current-balance-en-205/
• CFPB — Prepayment penalties: https://www.consumerfinance.gov/ask-cfpb/what-is-a-prepayment-penalty-en-1957/
• CFPB — Mortgage-servicer payment information: https://www.consumerfinance.gov/consumer-tools/mortgages/your-mortgage-servicer-must-comply-with-federal-rules/
• CFPB — Negative amortization: https://www.consumerfinance.gov/ask-cfpb/what-is-negative-amortization-en-103/

Source research refreshed September 21, 2026. Educational estimate only; not a lender statement, payoff quote, or financial advice.