Cycle Regularity Checker
Statistical spread of your last six cycles with the FIGO definitions of 'regular' and 'irregular'.
FIGO's modern definition replaced the myth that regular means same-length: up to 7–9 days of swing across six cycles is formally *regular*. Persistent irregularity is worth investigating (thyroid, PCOS and prolactin are the common, very treatable causes) — as data, six tracked cycles is exactly what a gynaecologist will ask for, so this number is your appointment prep.
Formula
For general information only. Pregnancy and infant care decisions must be guided by your treating clinician or midwife — always defer to their assessment.
Disclaimer: This tool is for general informational and estimation purposes only and is not professional financial, tax, accounting or legal advice. All figures are estimates — verify with a qualified professional before making decisions. Read the full disclaimer.
Statistical spread of your last six cycles with the FIGO definitions of 'regular' and 'irregular'. The Cycle Regularity Checker is a free, private irregular periods tool — every result computes instantly in your browser with no sign-up and no data upload.
About Cycle Regularity Checker
FIGO's modern definition replaced the myth that regular means same-length: up to 7–9 days of swing across six cycles is formally *regular*. It applies FIGO 2018: shortest-to-longest variation ≤ 7–9 days = regular. Use the Cycle Regularity Checker to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Cycle Regularity Checker
- 1Enter your details in the Cycle Regularity Checker input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Cycle Regularity Checker?
- ✓Instant irregular periods result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Munro MG et al., Int J Gynaecol Obstet 2018 — FIGO AUB System 1)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Cycle Regularity Checker work?+
FIGO's modern definition replaced the myth that regular means same-length: up to 7–9 days of swing across six cycles is formally *regular*. The calculation uses the formula: FIGO 2018: shortest-to-longest variation ≤ 7–9 days = regular. Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Cycle Regularity Checker accurate, and what is it based on?+
The method is traceable to authoritative sources: Munro MG et al., Int J Gynaecol Obstet 2018 — FIGO AUB System 1. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Cycle Regularity Checker free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is informational only. Always defer to your treating clinician or midwife for pregnancy and infant care decisions.
What can I use the Cycle Regularity Checker for?+
It's commonly used for irregular periods, cycle regularity, figo irregular cycles. Statistical spread of your last six cycles with the FIGO definitions of 'regular' and 'irregular'.
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