Period Date Calculator
The dates of your next six periods, with the fertile window marked in each cycle.
If your cycles are reasonably regular, the next few are easy to project. This lays out six cycles ahead so you can plan around them — and shows you what "regular" looks like written down, which is useful information to take to a doctor if it is not.
How this is worked out
A typical adult cycle runs 21 to 35 days, and 24 to 38 days is the range the International Federation of Gynecology and Obstetrics treats as normal. Bleeding usually lasts two to seven days. Cycles are often longer and less predictable in the first few years after periods start and in the years approaching menopause.
Worth a conversation with a doctor: cycles consistently shorter than 21 days or longer than 35, bleeding heavy enough to soak through a pad or tampon every hour for several hours, bleeding longer than seven days, bleeding between periods, or periods that stop for three months when you are not pregnant.
This calculator runs entirely in your browser. Nothing you enter is transmitted to us, saved on our servers, or shared with anyone.
Common questions
How do I count my cycle length?
From the first day of bleeding in one period to the day before bleeding starts in the next. Average three to six cycles for a number worth using.
Why is my period late?
Pregnancy, stress, weight change, heavy training, illness, travel across time zones, thyroid problems, PCOS and some medicines can all delay a period. A late period with a negative test that stays away is worth checking out.