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Finance & LoansGenerated accuracy model review: 2026-05-06
Credit Card 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 uses the NPER formula to determine the number of periods required to pay off a loan given a constant interest rate and payment amount. It assumes you stop adding new charges to the card.
Test cases
Default input regression check
Generated from the checked-in default inputs and calculate function.
Inputs
- Card Balance: $5,000
- Interest Rate (APR): 19.9%
- Monthly Payment: $200
Expected outputs
- Months to Payoff: 2y 9m
- Total Interest Paid: $1,600.00
Known limitations
- Assumes a fixed monthly payment and interest rate. Does not account for late fees or variable APRs.
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
- Card Balance accepts values in $.
- Interest Rate (APR) accepts values in %.
- Monthly Payment accepts values in $.
- Total Interest Paid 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 credit-card-payoff-calculator calculator definition.
Change log
2026-05-06
Published default regression test documentation and metadata fallbacks for Credit Card Payoff.
Calculator transparency
Accuracy pages are generated from checked-in calculator definitions and can be upgraded with curated review metadata over time.