Editorial policy
Health content earns trust through process. This is ours.
Sources
- First: clinical bodies and public health services — ACOG, FIGO, the NHS, the U.S. National Institutes of Health (NICHD), the Office on Women’s Health, WHO, Mayo Clinic and Cleveland Clinic.
- For numbers from research: peer-reviewed studies, named where they are used — for example Wilcox 1995 and 1999, and Bull 2019 (a large app-based dataset whose study was funded by the app’s maker, which we note where it is cited).
- Only for describing common experiences: medically reviewed consumer health articles such as WebMD’s — never for thresholds or when-to-see-a-doctor lines.
- Not as sources: forums, anonymous claims or manufacturer marketing. We read forums only to learn what readers ask.
Writing and review
Articles are researched and written by Mira Chen, the site's founder and editor, with the help of AI research and writing tools. Every draft, AI-assisted or not, is checked against the sources cited on the page, and calculator explanations against the code the tools run, before it is published. Every page carries a byline, a publication date and a last-reviewed date. Editorial fact-checking is not independent medical review, and we do not present this website as a medical diagnosis service.
Updates
Guides are re-reviewed at least every nine months and after material new guidance; tools are re-verified yearly. Every page shows its publication date and the date it was last updated. Readers can report errors to contact@onlineperiodcalculator.com; confirmed errors are corrected on the page and its updated date changes.
Independence
Editorial content is not influenced by advertisers or affiliates. Where we ever link to commercial products, the link is labeled. Our calculators' formulas and their limits are published on the methodology page for anyone to inspect.