About Online Period Calculator
Online Period Calculator is an independent health-information website, independently operated by Mira Chen, founder and editor, based in China.
Why this site exists
Period prediction tools have been around for decades, yet most ask you to hand intimate health data to an app account before doing thirty seconds of arithmetic. We think that trade is unnecessary. Every calculator on this site runs in your browser: no sign-up, and the dates you enter are not stored on a server or sold. Details are in the privacy policy.
Who is behind this site
All articles and tools on this site are researched, written, and maintained by Mira Chen. I am a health-content writer and editor — not a licensed medical professional. I built this site because cycle-tracking information online is often buried in jargon or locked behind apps, and I wanted a place where the underlying science is explained in plain language, with the sources shown.
This site is a personal editorial project. It is not operated by a hospital, clinic, or medical company, and there is no medical team behind it.
What we build
A growing family of cycle tools — period prediction, irregular-cycle ranges, late-period checks and more — each paired with plain-language explanations written to a published editorial standard and checked against sources like ACOG, the NHS, Mayo Clinic, Cleveland Clinic and WHO.
How we create content
Every article and calculator on this site follows the same documented workflow:
- Research — we start from primary and authoritative sources: peer-reviewed journals and guidance from organizations such as ACOG, WHO, and the NHS.
- Citation — key claims are linked to their sources, so you can check every reference yourself.
- Verification — before anything is published, it is checked against the standards described on our editorial policy and methodology pages.
- Corrections — when we get something wrong, we fix it on the page and update its date. You can report an error at any time using the contact details below.
How the site is paid for
- Advertising: the tools are free and the site is funded by ads. It has applied to Google AdSense, whose script already loads on every page.
- Analytics: we count visits with self-hosted, cookieless Plausible Analytics.
- What advertisers don't get: any say over what we write, or the dates you enter — the privacy policy lists exactly what each script receives.
What we are — and what we are not
- We are an independent editorial project that turns published research into plain-language articles and simple calculation tools.
- We are not a medical provider: nothing on this site is medical advice, diagnosis or treatment, and no page is reviewed by a doctor or other licensed clinician — checking a page against the sources it cites is editorial fact-checking, not medical review.
- Results are calendar estimates from the dates you enter — not a diagnosis, not a pregnancy test and not contraception.
- We are not affiliated with ACOG, the NHS, Mayo Clinic or any other source we cite.
Contact
We read every message and typically reply within a week. Email: contact@onlineperiodcalculator.com — or use our contact page. Correction requests, questions about our sources, and collaboration inquiries are all welcome at the same address; a clear subject line helps us route it faster.