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Finance & LoansGenerated accuracy model review: 2026-05-06
IRR Calculator 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 an iterative numerical method (Newton-Raphson) to find the discount rate (r) where: NPV = Σ [ CashFlow / (1+r)^t ] = 0.
Test cases
Default input regression check
Generated from the checked-in default inputs and calculate function.
Inputs
- Initial Investment: -$10,000
- Cash Flows: 3000, 4000, 5000, 6000
Expected outputs
- IRR: 24.89%
- NPV (at 10% Discount): $3,887.71
Known limitations
- IRR may fail or return multiple values if cash flows alternate signs multiple times (e.g. -, +, -, +).
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
- Initial Investment accepts values in $.
- Cash Flows accepts text values.
- IRR is displayed as a percentage.
- NPV (at 10% Discount) 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.
- Percent outputs are displayed with two decimal places.
Version history
1.0.0 - 2026-05-06
Generated accuracy and testing page from the current irr-calculator calculator definition.
Change log
2026-05-06
Published default regression test documentation and metadata fallbacks for IRR Calculator.
Calculator transparency
Accuracy pages are generated from checked-in calculator definitions and can be upgraded with curated review metadata over time.