Period Tracker

It adds your average cycle length to the start date of your last period. For example, with a 28-day cycle and a last period starting January 5, the next predicted period starts February 2. The next three cycles are predicted the same way.

The fertile window is the roughly 6 days each cycle when pregnancy is most likely: the 5 days before ovulation plus ovulation day itself. This tracker estimates ovulation as cycle length minus 14 days from the period start.

No. These are calendar estimates only, not contraception. Cycle timing varies naturally, and estimates are not reliable enough to prevent pregnancy. Use a proven contraceptive method and talk to a clinician.

Only if you tick the save box — then your inputs are stored in your own browser's localStorage on this device and never sent to a server. Unticking the box and reloading clears them.

See a clinician if your cycles are regularly shorter than 21 days or longer than 35 days, you miss periods, or anything about your cycle worries you. This tool is for information only, not medical advice.