Standards and methodology
Methodology
How we design, test and update calculators and their sources.
Standards and methodology
What you should know
The key information is presented below in a short, scannable format.
Key point 1
Calculation engines are separated from their interfaces and tested with typical, boundary and invalid cases. Decimal arithmetic is used for money and rounding happens at a documented stage.
Key point 2
Legal, tax, medical and education parameters require a source, applicable year and review date. Unverified tools remain drafts and are excluded from the sitemap.
Key point 3
Calculator inputs are processed in the browser by default. Analytics events never include raw inputs or results.
Last reviewed: 3 August 2026.
Useful links
Continue exploring
Read the core pages behind the service or go directly to the tool catalogue.