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Finance & LoansGenerated accuracy model review: 2026-05-06
Mortgage Payoff accuracy and testing
This page documents how Calwarden builds trust for this calculator: source notes, regression-style default tests, limitations, assumptions, unit handling, rounding, and visible change history.
Formula source
- The calculator runs two amortization schedules. The first pays only the required amount. The second adds your extra payment to the principal every month. It tracks how quickly the balance hits zero in both scenarios.
Test cases
Default input regression check
Generated from the checked-in default inputs and calculate function.
Inputs
- Current Balance: $250,000
- Interest Rate: 6.5%
- Remaining Term: 30 Years
- Extra Monthly Payment: $200
Expected outputs
- Time Saved: 7 years, 11 months
- Interest Saved: $97,618.12
- New Payoff Time: 22 years, 1 months
Known limitations
- Assumes the extra payment amount stays constant for the entire remaining term. Does not account for lump sum payments.
Assumptions
- Inputs are interpreted exactly as entered in the calculator form.
- The calculation runs locally in the browser using the current checked-in calculator definition.
Unit handling
- Current Balance accepts values in $.
- Interest Rate accepts values in %.
- Remaining Term accepts values in Years.
- Extra Monthly Payment accepts values in $.
- Interest Saved is displayed as currency.
Rounding rules
- Number displays use up to 2 decimal places in the calculator UI.
- Currency outputs are displayed with standard US dollar formatting.
Version history
1.0.0 - 2026-05-06
Generated accuracy and testing page from the current mortgage-payoff-calculator calculator definition.
Change log
2026-05-06
Published default regression test documentation and metadata fallbacks for Mortgage Payoff.
Calculator transparency
Accuracy pages are generated from checked-in calculator definitions and can be upgraded with curated review metadata over time.