Ovulation Calculator
Enter your last menstrual period and average cycle length to estimate your ovulation date and fertile window — the days when conception is most likely.
Calculate Your Ovulation
Default is 28 days. If your cycle is longer or shorter, adjust this for a more accurate estimate.
How It Works
Ovulation typically occurs about 14 days before the next expected period. For a 28-day cycle, this is day 14. For a 32-day cycle, this is day 18.
The Formula
Ovulation date = LMP + (cycle length − 14)
Fertile window = 5 days before ovulation to 1 day after ovulation
This accounts for sperm survival (up to 5 days) and egg viability (12-24 hours).
Your Fertile Window
The fertile window is the 6-day period when conception is most likely. It includes the 5 days before ovulation and the day of ovulation itself.
| Phase | Days | Conception Likelihood |
|---|---|---|
| 5 days before ovulation | Day -5 to Day -1 | Moderate |
| Day of ovulation | Day 0 | Highest |
| 1 day after ovulation | Day +1 | Low |
Tips for Tracking Ovulation
- Basal body temperature (BBT): Your BBT rises slightly (0.5-1°F) after ovulation. Tracking BBT over several cycles can help predict ovulation.
- Cervical mucus: Around ovulation, cervical mucus becomes clear, stretchy, and slippery — like egg whites.
- Ovulation predictor kits (OPKs): These detect the luteinizing hormone (LH) surge that occurs 24-36 hours before ovulation.
- Calendar method: Track your cycles over several months to identify patterns.
When to Talk to Your Clinician
Contact your healthcare provider if:
- Your cycles are irregular (varying by more than 7 days)
- You have been trying to conceive for 12 months (or 6 months if you are over 35)
- You have questions about your fertility or ovulation
Related Tools
- Conception Date Calculator — estimate your conception window
- Gestational Age Calculator — how many weeks pregnant are you?
- Pregnancy Test Timing — when to take a pregnancy test