How the amortization schedule is built
Use this tool to see how a fixed monthly mortgage payment is split between interest and principal and how the remaining balance changes month by month.
The calculator first solves the fixed monthly payment for a fully amortizing loan. For each month, interest equals the opening balance multiplied by the monthly rate. The rest of that month’s scheduled payment reduces principal. The ending balance becomes the next month’s opening balance, and the process repeats until the balance reaches zero or the entered term ends.
Payment = L × r ÷ [1 − (1 + r)^−n]The same fixed-payment equation used for a standard amortizing mortgage.
Interest = opening balance × annual rate ÷ 12 ÷ 100Interest normally declines as the balance falls.
Principal = scheduled payment − monthly interestThe principal portion generally grows over time in a fixed-rate schedule.
Enter the current or proposed loan balance.
Enter a fixed annual note rate and the total number of repayment months.
Review the first months to see the interest-heavy starting mix.
Use the schedule and totals to understand balance reduction over your expected holding period.
Best used for
- Explaining why early payments contain more interest
- Checking the balance after a future month
- Comparing total modeled interest across different terms
What this tool does not answer
- The schedule assumes a fixed rate and monthly payment timing.
- Taxes, insurance, HOA and mortgage insurance are not part of the amortization table.
- Servicer rounding, payment dates, fees and irregular extra payments can change an actual payoff statement.
How to read a sample result
Illustrative example: $300,000 at 6% for 360 months produces a scheduled payment of about $1,798.65. Over the full modeled term, total interest is about $347,514.57, with the balance declining to zero after 360 scheduled payments.
The methodology below explains how this calculator treats the inputs and assumptions. Replace the sample values with your own planning figures. Results are estimates, not quotes, approvals, disclosures or recommendations.
Inputs and units
Principal, note rate and repayment term. All currency entries are U.S. dollars. Percentage fields take a number such as 6 for six percent, not 0.06. Repayment terms marked in months use whole months; horizons marked in years use whole years.
Calculation workspace
Enter your own figures in the calculator above. The starting values are examples only. No personal identifiers are needed to run a scenario.
How to interpret the result
Read every result together with the assumptions you entered. Changing an input changes the scenario, not product availability. Displayed amounts are rounded for readability.
Assumptions and limitations
The schedule uses monthly interest and unrounded internal calculations. Actual servicer rounding, dates and escrow are not reproduced.
Review more than one scenario
Run a base case and then change one uncertain input at a time. Compare a shorter holding period, a higher cost or a different repayment term where those inputs are supported. Record which costs have not been entered. A precise-looking number can still rest on uncertain assumptions.
Invalid inputs and error recovery
If an input is missing or outside the calculator’s supported range, the page will ask you to correct it. Use negative values only in fields that explicitly allow them. A calculation error is not a credit decision.
Model documentation
The calculator methodology explains the inputs, assumptions and supported models. Use the result for planning and compare it with the provider’s written terms and applicable disclosures before making a decision.
Choose a product for your calculation
Use these comparisons for planning; final eligibility, pricing and terms are set by the provider.
Program references and comparison sources
CFPB: Loan Estimate explainer — Comparison of covered mortgage disclosures, cash to close, points, lender credits and monthly costs.
CFPB: Understand the different kinds of loans available — Loan structures, terms and repayment risks; not provider-specific eligibility.
Check the linked source for its effective date and applicable scope. A source link is not a lender partnership or an individual offer.