How our calculators work

Every calculator on this site is built from two parts: a rule pack and an engine. A rule pack is a data file that holds the numbers a state's law sets, such as guideline percentages, income caps, and interest rates. Each number in a pack carries a citation to an official source, usually the statute or the state agency that publishes it, plus the date we last reviewed it.

The engine is the part that does the math. It reads your inputs and the rule pack, then applies the state formula step by step. Nothing is hidden: the result shows each line of the calculation, and each line links to the source it comes from. If an input falls outside what the formula covers, the tool says so instead of guessing.

Before a state calculator goes live, we write test scenarios by hand from the statute. Each scenario works the formula out on paper, records every step, and states the expected result. There are 510 scenarios across all 50 states and DC. 61 match official calculator or estimator outputs within the published verification tolerance, and 3 match official worked examples. Another 1 scenario records an official refusal to produce a result, not a numeric amount match. The remaining 445 are source-derived checks, not independent official-tool confirmations. Of those, 152 still need an official calculator, worksheet, or interpretation cross-check. Today, 510 of the 510 evidence scenarios run as full engine regression fixtures on each change, including explicit fail-closed tests. A historical official comparison is not a guarantee that every branch of a state calculator is independently verified. The verification registry shows the count for each jurisdiction.

The state map, table, and calculator directory cover all 51 jurisdictions: 50 states and DC. Where a formula needs inputs a standardized example does not define, the table directs you to the state page with the reason. We do not publish an invented figure to fill a blank.

Arrears-interest research uses a separate evidence model because a calculator parameter is not a complete legal ledger rule. The 50-state and DC arrears-interest dataset records legal scope, charge type, method evidence, historical-rate needs, and named open questions. A missing numeric rate stays blank rather than becoming zero.

Every result carries the same disclaimer stack: these are estimates, the court or state agency calculation controls, this site does not give legal advice, and it is not affiliated with any government agency. Guideline support is also only part of most orders; judges can and do deviate.

If you find a number that does not match an official source, please contact us. Dated corrections and rule changes are listed on the updates page.