Frequently asked questions
How reliable are period predictions with irregular cycles?
For irregular cycles, predictions based on a single average cycle length are less reliable. The more your cycle varies month to month, the wider the margin of error. Tracking at least 3 to 6 months of data improves accuracy. If cycles vary by more than 7 to 9 days, consult a healthcare provider.
What is a normal cycle length?
Normal menstrual cycles range from 21 to 35 days, with 28 days being the commonly cited average. Cycles shorter than 21 days (polymenorrhea) or longer than 35 days (oligomenorrhea) may warrant medical evaluation, especially if they are a change from your usual pattern.
Does cycle length change with age?
Yes. Cycles tend to be longer and more irregular in the first few years after menarche, become more regular in the 20s and 30s (often shortening slightly), and then become irregular again in the years approaching menopause (perimenopause, typically mid-40s).
Why does my period arrive early or late sometimes?
Stress, illness, travel, weight changes, intense exercise, and hormonal fluctuations can all shift ovulation timing, which directly affects when your period arrives. A variation of 1 to 5 days is considered normal. Consistently irregular timing warrants medical evaluation.
Can I get pregnant on my period?
While unlikely for most women, it is possible, especially with short cycles. If your cycle is 21 days, you may ovulate around day 7. Since sperm can survive up to 5 days, intercourse during a period ending on day 5 could overlap with the fertile window.
When should I see a doctor about my cycle?
Seek medical advice if your period is consistently shorter than 21 or longer than 35 days, if you miss periods without pregnancy, if bleeding lasts more than 7 days, if you experience very heavy bleeding (soaking through protection hourly), or if periods suddenly become very painful.