Mortgage Amortization Calculator and Payment Schedule
Build an estimated amortization schedule showing the balance, principal, and interest portions of a fixed-rate mortgage over time.
Inputs and calculation method
- Original mortgage principal
- Annual interest rate
- Loan term
- Optional extra-payment assumptions
The scheduled payment is calculated once for a fixed-rate loan. Each month, interest is estimated from the outstanding balance; the remaining payment reduces principal.
Core formula: Monthly interest = current principal balance × monthly rate; principal paid = scheduled payment − monthly interest.
How to interpret the estimate
At the beginning of a long mortgage, more of each payment generally goes to interest. As the balance declines, the principal portion increases.
Change one assumption at a time to understand which input has the greatest effect. Use exact figures from a lender disclosure, statement, pay record, account terms, or business records whenever possible. Calculator output is rounded and may differ from institution-specific calculations.
How to use this calculator effectively
Use exact figures from a lender or property estimate when available, then build a conservative scenario that allows for rate, tax, insurance, and maintenance uncertainty.
An amortization schedule explains how a fixed payment is divided between interest and principal over time. Use it to locate the projected balance at a future sale, refinance, or payoff date and to see how much interest is concentrated in the earlier years. The schedule is especially useful when comparing terms or evaluating an extra-payment strategy.
- Step 1: Original mortgage principal. Use a value from a current statement, written quote, account record, or documented plan whenever possible.
- Step 2: Annual interest rate. Use a value from a current statement, written quote, account record, or documented plan whenever possible.
- Step 3: Loan term. Use a value from a current statement, written quote, account record, or documented plan whenever possible.
- Step 4: Optional extra-payment assumptions. Use a value from a current statement, written quote, account record, or documented plan whenever possible.
What changes the result most
- Starting balance: every scheduled interest calculation begins with the outstanding principal.
- Interest rate: the monthly rate determines how much of each payment is consumed before principal is reduced.
- Term and payment count: a longer schedule spreads principal over more payments and usually increases lifetime interest.
- Extra principal and timing: additional amounts applied early reduce the balance used for many later interest calculations.
Practical decision guide
Review annual totals rather than only the first and last payments. Note the balance at the dates that matter to your plan, such as five years from closing or the end of a fixed-rate period. When comparing two loans, include upfront costs and verify that both schedules begin with the same financed amount and payment timing.
Questions to ask before relying on the result
- Which input is documented and which one is only an assumption?
- How does the result change under a more conservative rate, cost, payment, or time horizon?
- What cash-flow, risk, tax, legal, or contractual factor is not represented by the formula?
Common mistakes to avoid
- Adding escrow payments to principal reduction.
- Assuming every dollar above the regular payment is automatically applied to principal.
- Comparing schedules with different starting balances but focusing only on rates.
- Expecting an estimate rounded monthly to match a lender’s daily-interest or payment-date calculation exactly.
Limitations and how to verify the estimate
The schedule assumes the entered rate and payment pattern remain unchanged. Late payments, payment-date changes, recasting, modifications, adjustable rates, fees, and servicer rounding can produce a different balance.
Recheck the calculation when an input changes and compare the output with the applicable statement, disclosure, contract, plan document, or official source. Do not use a calculator result as a substitute for individualized financial, tax, legal, lending, investment, insurance, payroll, or accounting advice.
Save the date, inputs, and purpose of each scenario. That record makes later comparisons more reliable and helps explain why a result changed. When comparing alternatives, use the same measurement period and cost definitions; otherwise a seemingly better result may come from inconsistent assumptions rather than a genuine financial advantage.
Official references and further reading
- Consumer Financial Protection Bureau: Owning a home — Official tools and explanations for mortgage shopping, loan estimates, closing costs, and homeownership decisions.
Frequently asked questions
Why does the balance fall slowly at first?
Interest is calculated on the larger early balance, so less of the fixed payment is available to reduce principal.
Does the schedule include escrow?
An amortization schedule normally covers principal and interest only. Escrowed taxes and insurance do not reduce the loan balance.
Will my lender’s schedule match exactly?
Small differences can result from rounding, payment dates, daily-interest conventions, fees, and loan-specific rules.
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Last technical review: June 26, 2026. Methodology is provided for transparency. This calculator is educational and does not provide financial, tax, legal, investment, lending, insurance, or accounting advice. Read the methodology and calculator disclaimer.