Put your luteal phase on the calendar.
When does the second part of your cycle start and end on paper? Enter its assumed length. We show the corresponding dates in your current calculated cycle.
Your cycle takes shape here
Enter your last period start in the form. Your calculated date ranges will appear here.
This ring is only an example of a 28-day cycle.
Your inputs stay when you switch views. Opening a new page starts with empty inputs. Open this view on its own page
An orientation based on your inputs
The calculator repeats your cycle length. If your last period started further back, it shows the calculated cycle that contains today. It does not detect actual bleeding or phases. The results are not suitable for contraception, diagnosis or identifying ovulation.
Good to know
Does this calculator find my luteal phase length?
No. That duration is your input. The calculator derives the dates from it: a 28-day cycle with a 14-day luteal phase places it at cycle days 15 to 28.
How are the start and end calculated?
The luteal phase sits at the end of the calculated cycle. It starts at cycle length minus luteal phase length plus 1 and ends on the last cycle day. For a 28-day cycle starting on 1 September, a 14-day luteal phase runs from 15 to 28 September.
What does the default of 14 days mean?
It is a starting value for the calculation. It proves neither the length of your actual luteal phase nor that ovulation took place. You can enter any whole number from 8 to 18 days for the model.
Why have the dates moved beyond the month I entered?
If one or more of your entered cycle lengths have passed since your period start, the tool continues to the current calculated cycle. Its full date range appears above the phase band.
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In the app you record how you actually feel and recognise your own patterns across weeks and cycles. No points, no streaks, no grading.
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