How we build
Tools that show their work.
Every calculator names the statute or rule it implements, links the primary source, and ships with a unit-test suite on the underlying formula. These are planning tools, not professional advice.
Statute-cited
Every formula maps to a specific statute, rule, or filing — cited inline with a primary-source outbound link so you can verify the source yourself.
Unit-tested
Every formula is a pure function with a regression test suite. The math is deterministic, the inputs are visible, and the tests live in the repo next to the calculator.
Reviewed against statute
Pages carry a visible "last reviewed against" stamp and are refreshed when the statute, rule, or filing changes. These are tools — for binding advice, consult a licensed professional.
Who reviews these
The Fennec Lab Editorial TeamStatute-cited · Unit-tested
The Fennec Lab's calculators are reviewed against the primary statute, rule, or filing they implement, and every formula ships with a regression test suite that lives in the open repo. Pages carry a visible "last reviewed against" stamp and are refreshed when the underlying rule changes. These are planning tools, not legal, tax, insurance, or financial advice — consult a licensed professional in your jurisdiction before acting on a result.
How a result is produced
From statute to a number you can trust
1. Source the rule
Each calculator starts from the primary statute, administrative rule, or IRS provision that governs the math — cited inline with a primary-source link, and surfaced on every page under the “Reviewed against” stamp.
2. Encode the formula as a tested function
The formula is a pure function over typed inputs. It ships with a regression test suite that lives next to the calculator in the public repo, so the math is deterministic and independently checkable.
3. Review against the source and date it
Before publishing, the output is checked against the cited rule. Each page records a “last reviewed against” date and is refreshed when the underlying statute, rule, or filing changes.
Why we build these
These tools exist to answer a real question in place — “what does this statute actually compute for my numbers?” — for the person using the calculator, not to rank for a keyword. Every page is meant to be the endpoint for that question: the math, the source, and the limits on one screen.
On how the work is made: calculators are drafted with software assistance and then reviewed against the cited primary source before publication. The verifiable claims are the statute citation and the open test suite — not an appeal to authority.
Sources & corrections
Primary sources are linked on each calculator page. If a citation is out of date or a result looks wrong, the formula and its tests are in the open repository so the discrepancy can be traced to the exact line of math. See our disclosures for affiliate and partnership relationships, and our privacy policy for how inputs are handled (they are not collected — the math runs in your browser).