PulseLoopHealth

Period Tracker

Predict your next period, ovulation, and fertility window.

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Understanding your cycle

The numbers behind the predictions

Typical cycle length
24 to 38 days
Typical bleeding
3 to 7 days
Ovulation
about 14 days before the next period
Egg survives
12 to 24 hours after release
Sperm survive
up to 5 days
Fertile window
about 6 days

How a period is predicted

Counting starts on the first day of bleeding — that is day one. Your next period is estimated by adding your average cycle length to that date. The more cycles you log, the closer the average gets to your own pattern rather than a textbook one.

Ovulation is estimated backwards, not forwards: it happens roughly 14 days before your next period starts, so it moves with your cycle length rather than always landing on day 14.

Why the fertile window is six days

An egg only survives 12 to 24 hours after it is released, but sperm can survive up to five days in the reproductive tract. Together that makes roughly a six-day window — from about five days before ovulation to one day after.

This is why predictions are useful for planning but are not contraception. Cycle length varies, ovulation shifts with it, and an estimate is not a guarantee.

What counts as irregular

Cycles vary from month to month, and some variation is normal — especially in the first years after periods start and in the years approaching menopause. Worth raising with a doctor:

  • Periods less than 21 days or more than 35 days apart
  • Bleeding that lasts longer than seven days
  • Flow much heavier or lighter than usual for you
  • Severe pain, cramping, nausea or vomiting with your period
  • Bleeding between periods
  • Three missed periods in a row
  • No period by age 16

Stress, weight change, travel, illness, hormonal contraception and thyroid or polycystic ovary conditions can all shift a cycle. A tracker records the pattern; it does not explain the cause.

Sources