🌸 Ovulation & Pregnancy Calculator
Find your fertile window and ovulation day — or calculate your pregnancy due date and trimester timeline. Enter your last period date to get started.
Most cycles are 21–35 days. Average is 28 days.
Current Cycle
Fertile Window
Mar 5 – Mar 11
Ovulation Day
Tue, Mar 10, 2026
Next Period
Tue, Mar 24, 2026
| Period Start | Fertile Window | Ovulation |
|---|---|---|
| Tue, Mar 24, 2026 | Mar 5 – Mar 11 | Tue, Mar 10, 2026 |
| Tue, Apr 21, 2026 | Apr 2 – Apr 8 | Tue, Apr 7, 2026 |
| Tue, May 19, 2026 | Apr 30 – May 6 | Tue, May 5, 2026 |
🌸 Predictions are based on a 28-day cycle. Actual ovulation can vary. For best results, track basal body temperature (BBT) and cervical mucus alongside this calculator.
💡 Have suggestions? Help us improve this calculator!
Send FeedbackHow Does Ovulation Work?
Ovulation is the release of a mature egg from one of the ovaries. It occurs once per menstrual cycle, typically around 14 days before your next period. After the egg is released, it travels down the fallopian tube and is viable for fertilisation for only 12–24 hours.
Because sperm can survive in the female reproductive tract for up to 5 days, the fertile window extends from 5 days before ovulation to the day of ovulation itself — giving a 6-day window for conception.
How to Calculate Your Ovulation Date
The most common method is to subtract 14 days from the expected start of your next period. For example, in a 28-day cycle:
- LMP (Last Menstrual Period) start: Day 1
- Ovulation: Day 14 (28 − 14)
- Next period: Day 28
For a 30-day cycle, ovulation typically occurs around day 16. For a 35-day cycle, around day 21.
How is the Due Date Calculated?
The standard method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period. This gives the estimated due date (EDD), also called the "estimated date of confinement" (EDC).
Only about 5% of babies are born on their exact due date. Most births occur within 2 weeks before or after. An ultrasound scan in the first trimester (weeks 8–12) gives the most accurate dating.
Pregnancy Trimesters
- First Trimester (Weeks 1–13): Organ formation, highest risk of miscarriage. Morning sickness common.
- Second Trimester (Weeks 14–26): Most comfortable phase. Baby movements felt from ~18–20 weeks.
- Third Trimester (Weeks 27–40): Rapid growth, preparation for birth.
Frequently Asked Questions
Can I get pregnant outside the fertile window?
It's very unlikely but not impossible. Sperm generally survive 3–5 days, and ovulation timing can shift due to stress, illness, or cycle irregularities. The only reliable way to avoid pregnancy is consistent use of contraception.
What affects ovulation timing?
Stress, intense exercise, low body weight, thyroid disorders, PCOS (polycystic ovary syndrome), and certain medications can all shift ovulation timing. If your cycles are irregular, tracking with BBT (basal body temperature) or LH test strips gives more precise data.
How accurate are ovulation calculators?
Ovulation calculators are most accurate for women with regular cycles. They provide an estimate, not a guarantee. For conception or contraception purposes, combine this tool with physical signs: cervical mucus changes (clear, stretchy, egg-white texture), mid-cycle spotting, or LH surge tests.