If your period lasts 3 days, the timing of your ovulation depends primarily on the length of your overall menstrual cycle, not just the duration of your period. Ovulation typically occurs about 10 to 16 days before the start of your next period. In a typical 28-day cycle (counting from the first day of your period), ovulation usually happens around day 14. Since your period lasts 3 days, your ovulation would generally be around 11 to 17 days after the first day of your period, depending on your total cycle length. Here are some key points:

• The menstrual cycle length varies widely, commonly between 21 to 35 days.
• Ovulation happens roughly in the middle of the cycle, but not exactly 14 days for everyone.
• The luteal phase (time from ovulation to next period) is relatively constant at about 14 days.
• Thus, ovulation timing depends on the follicular phase length, which varies more.
• If your cycle is about 28 days, you'll ovulate around day 14.
• If it's shorter or longer, ovulation moves accordingly (shorter cycles ovulate earlier, longer cycles ovulate later).

If counting from the first day of your period, and your period lasts 3 days, you typically ovulate between day 11 and day 17 of the cycle, depending on your overall cycle length.

To be more precise, knowing your average cycle length is important. For example:

Cycle Length (days)| Approximate Ovulation Day (from period start)
---|---
21| Day 7
26-28| Days 12-14
30| Day 16
35| Day 21

The 3-day period length mainly determines the start of the cycle, but ovulation timing depends on the overall cycle length.