Each calculator passes four stages before it is published, and the same stages again whenever it changes.
- Specification. The author writes down the formula, units, valid input ranges and the source for every constant and threshold.
- Automated verification. Unit tests check the implementation against worked examples from the source, including boundary values (for example a BMI of exactly 25.0).
- Expert review. A qualified reviewer in the field checks the formula, the thresholds and every sentence of interpretation. They sign off with their name and the date.
- Accessibility and usability checks. Each tool is tested with a keyboard and a screen reader, on mobile and in dark mode.
Reviews are repeated at least every 12 months. The date of the most recent review appears under the title of every page.