Period calculator
High-volume query, deliberately thin on drama: next period and the following two starts. Support infrastructure for the dating site — not a Flo competitor. Estimate only — not medical advice.
Enter a date to see an estimate.
What this page does
Shares the next-period engine. Soft link to pregnancy-test timing if you are late and testing — no scare funnel, no gender upsells mid-page.
Brand trust still lives on IVF / reverse / implantation pages.
When to use
Quick next-period math; sharing a date without installing an app.
When not to
Pregnancy dating (use weeks/EDD tools). Conception courtroom stories.
Assumptions
Browser-only planning arithmetic. Defaults are disclosed on the page. Ultrasound and clinic policy override this tool.
Examples
LMP Jun 12, 2026 · cycle 27 → Next Jul 9, 2026.
LMP Jun 12, 2026 · cycle 28 → Next Jul 10, 2026.
Gotchas
Clinic dating after ultrasound can differ from browser math — the clinic wins for medical decisions.
Wrong input dates (retrieval vs transfer, spotting vs true LMP) slide every result.
Estimate only — not medical advice.
How this is calculated
The math stays in your browser. Enter the dates you actually know, read the estimate, and treat clinic ultrasound dating as the authority when it disagrees.
Nothing here is medical advice, a diagnosis, or a substitute for prenatal care.
- Enter the date(s) or numbers this page asks for.
- Check the assumptions under the result and on Methodology.
- Compare with your clinic portal if you have one.
- Use related tools if you only have a different kind of date.
- Confirm medical decisions with your clinician.
See Methodology for the dating table used across PregDateBase.
Related calculators
Next period twin: next period calculator. If late and testing: pregnancy test timing.
See also: next period calculator, menstrual cycle calculator, and pregnancy test timing calculator.
FAQ
- How does a period calculator work?
- Last period + cycle length.
- Why is my period late?
- Many reasons — this calculator cannot triage.
- Is this a period tracker app?
- No.
- Irregular cycles?
- Only with wide uncertainty; averages mislead.
- Pregnancy dating here?
- No — use weeks/EDD tools.
- Is this medical advice?
- Estimate only — not medical advice. Confirm dating, testing, and medical decisions with your clinic.