When do I ovulate on a 28-day cycle?
Ovulation usually happens about 14 days before the next period starts. On a 28-day cycle, the next period starts on day 29, so ovulation is most likely around day 14 (counting the first day of your period as day 1). A 28-day cycle is within the typical range; cycles from about 21 to 35 days are common in adults.
Your fertile window on a 28-day cycle
Sperm can live for up to five days and an egg for about a day, so the fertile window is the five days before ovulation plus ovulation day: cycle days 9 to 14. The best days to try are days 12 to 14.
| Cycle day | Fertility |
|---|---|
| Day 7 | Low chance |
| Day 8 | Low chance |
| Day 9 | Fertile |
| Day 10 | Fertile |
| Day 11 | Fertile |
| Day 12 | Most fertile |
| Day 13 | Most fertile |
| Day 14 | Ovulation (most fertile) |
| Day 15 | Fertility falls quickly |
| Day 16 | Fertility falls quickly |
| Day 17 | Fertility falls quickly |
Does my period length matter?
No — whether your period lasts 3, 5 or 7 days, ovulation on a 28-day cycle is still around day 14. With a 5-day period, that is about 9 days after your period ends.
How sure is this?
The 14-day rule is an average: the second half of the cycle usually lasts 12 to 16 days, so ovulation on a 28-day cycle could be anywhere from about day 12 to day 16. Ovulation tests, which detect the LH surge, or temperature charting can confirm your own pattern. If your cycles vary a lot, enter your average cycle in the Ovulation Date Calculator and treat the dates as approximate.
Other cycle lengths
25-day cycle · 26-day cycle · 27-day cycle · 29-day cycle · 30-day cycle · 31-day cycle