Know Your Cycle, Plan Ahead

Once you know your average cycle length, the next period is simple arithmetic — and so are the dates that matter around it. This period calculator projects your next periods, ovulation day, fertile window, and a due date if you're trying to conceive.

The 14-Day Anchor

Ovulation estimates rest on one reliable fact: the luteal phase between ovulation and your next period is almost always 13–15 days, regardless of total cycle length. Counting back 14 days from the predicted period gives the best calendar-based ovulation estimate.

Plan or Conceive

Use the fertile window to time intercourse for conception, or avoid those days if you're not trying — but remember calendar methods alone are not reliable contraception. Regular cycles make predictions accurate; irregular ones call for tracking methods.