Period Calculator
Calculate your next period date, ovulation day, and fertile window. Track your menstrual cycle and plan ahead.
Frequently Asked Questions
- Next period = Last period start date + Cycle length. Example: last period started April 1, cycle is 28 days โ next period expected April 29. The average cycle is 28 days but 21โ35 days is normal.
- Ovulation typically occurs 14 days before your next period, not necessarily mid-cycle. For a 28-day cycle: around day 14. For a 32-day cycle: around day 18. For a 24-day cycle: around day 10. This calculator shows your estimated ovulation window.
- The fertile window is the 6 days leading up to and including ovulation. Sperm can survive 3โ5 days in the reproductive tract, so you can conceive from intercourse a few days before ovulation. An egg survives only 12โ24 hours after release.
- A normal menstrual cycle is 21โ35 days, with 28 days being the average. Cycle length is counted from the first day of one period to the first day of the next. Cycles shorter than 21 or longer than 35 days may warrant a conversation with a healthcare provider.
- Most periods last 3โ7 days. Heavy flow typically occurs in the first 1โ3 days and lightens toward the end. Total blood loss per cycle is usually 20โ80 mL. Periods lasting more than 7 days or with very heavy flow may indicate an underlying condition.
- Common causes: pregnancy (most important to rule out), stress, significant weight change, intense exercise, illness, thyroid issues, PCOS, or perimenopause. A cycle can vary by ยฑ7 days from month to month and still be considered normal.
- It's unlikely but possible. Sperm can survive 5 days, and if you have a short cycle (21 days) and ovulate early, sperm from intercourse during your period could survive until ovulation. If you're not trying to conceive, use contraception throughout the cycle.
- This calculator is based on average cycle patterns and is suitable for planning and awareness only. Ovulation can shift by several days due to stress, illness, or hormonal fluctuations. For fertility planning or contraception, this should not replace medical guidance or ovulation testing.