Period calendar

How is a period date calculated?

Your next period is estimated by adding your cycle length to the first day of your last period. A cycle is the time from the first day of one period to the first day of the next, and for most people it ranges between 21 and 35 days. If your cycle changes a little each month, an average of the last few months gives a more accurate estimate.

The phases of your cycle

The cycle moves through the period, the follicular phase, ovulation and the luteal phase. The fertile window is the few days around ovulation. This calendar shows which day of your cycle you’re on right now and your upcoming dates — as an estimate, without judging your body.

Frequently asked questions

How is the period date calculated?

Your next period is predicted by adding your cycle length to your last period. For example, in a 28-day cycle, 28 days are added to your last period. If your cycle varies, an average of the last few months gives a more accurate result.

How long does a period usually last?

A period usually lasts about 2–7 days, and it is normal for this to differ from person to person. Bleeding that is much heavier or longer than usual over time is worth discussing with your doctor.

How many days is a normal cycle?

Cycles usually range from 21 to 35 days and vary from person to person — all normal. Your period itself most often lasts 2–7 days. If you notice a marked or lasting change, it is worth talking to your doctor.

Does the calendar work if my cycle is irregular?

With irregular cycles a single estimate is less reliable, but logging for a few months reveals the pattern and improves predictions. WeTime learns this for you automatically.

Other tools: Ovulation calculator · Pregnancy calculator · Due date calculator