Enter your recent cycle lengths to find your average cycle, see whether your cycles look regular, and predict your next period.
Average cycle length
28 days
Cycle regularity
Your recorded cycles look regular
Next predicted period
—
Enter your last period date to see your next predicted period.
How to use this tracker
Enter the first day of your most recent period, then fill in the length of your recent cycles in days (the number of days from one period start to the next). The tracker works best with at least two cycle lengths — add more for a more representative average. The pre-filled values (28, 29, 27) are examples; replace them with your actual numbers.
Understanding your result
The average cycle length is calculated from the lengths you enter. Regularity is assessed by comparing how much your cycles vary: a variation of 4 days or less is shown as regular, more than 4 days as irregular. These are informational observations, not medical assessments. The next period prediction is based on your average cycle length from your last period date.
Disclaimer
Menstrual cycles and ovulation timing vary significantly between individuals and from month to month. These predictions are statistical estimates and should not be used as a sole method of contraception or fertility planning. This is not medical advice. If you are trying to conceive, struggling to conceive, or have concerns about your cycle, consult a gynaecologist or healthcare provider.
Track your cycle in OptiAI
Log periods, track your cycle history over time, and get predictions in context with the rest of your health data in OptiAI.
Frequently asked questions
What is a normal cycle length?
A typical menstrual cycle ranges from 21 to 35 days, measured from the first day of one period to the first day of the next. The widely cited 28-day cycle is an average — most people fall somewhere in the 21–35 day range, and some variation from month to month is common.
What does irregular mean here?
This tool flags cycles as irregular when the standard deviation across your entered lengths is greater than 4 days. That is a statistical observation based on the numbers you entered — it is not a medical diagnosis. Many things can affect cycle length including stress, travel, sleep changes, and illness. If you are concerned about irregular cycles, speak with a healthcare provider.
Is this medical advice?
No. This calculator provides estimates for informational purposes only. Always consult a qualified healthcare professional before making decisions about your health, contraception, or fertility planning.
Organize your whole life in one intelligent place
OptiAI brings goals, money, health, travel, family, and planning together — with AI that understands your context.