Finance · Mortgage
Amortization Schedule
Build a monthly amortization path with optional extra principal and exportable schedule data.
Last reviewed: February 18, 2026
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What this calculator does
Build a monthly amortization path with optional extra principal and exportable schedule data.
How it's calculated
- Inputs are validated before running the calculator-specific compute() function.
- Core math is deterministic and implemented in src/lib/calculators/amortization-schedule.ts.
- Results are recalculated instantly as values change and are shareable via query parameters.
- Disclosure assumptions and limitations are shown on-page for decision context.
Example
Example scenario: Loan amount = 450000 USD; Interest rate = 6.25 %; Term = 30 years; Extra principal per month (optional) = 0 USD. Sample output: Monthly payment (scheduled): $2,770.73
Common mistakes
- Using optimistic rates or appreciation assumptions without testing a conservative case.
- Ignoring taxes, insurance, HOA, or maintenance in monthly cost planning.
- Treating modeled outputs as guaranteed quotes rather than planning estimates.
- Not comparing at least two scenarios before making a financing decision.
- Skipping professional review for legal, tax, underwriting, or insurance details.
FAQs
Why does interest dominate early years?
In fixed-rate amortization, interest is calculated on higher starting balance, so early payments carry more interest.
How does extra principal help?
Extra principal lowers balance faster, which reduces future interest and can shorten payoff timeline.
Can I export this schedule?
Yes, use the CSV export in Insights or the result export actions for spreadsheet workflows.
Does this include taxes or insurance?
No. This schedule tracks loan principal and interest only.
Will my lender schedule match exactly?
Lender systems may differ slightly in timing and rounding, so treat this as a planning approximation.