How the Calculator Works
Enter Your Data
Provide your last period date, average cycle length, and period duration. All calculations happen locally on your device for complete privacy.
Calculate Ovulation
We calculate your ovulation date using the standard method: cycle length minus 14 days. This gives us your most likely ovulation day.
Identify Fertile Window
Your fertile window includes 5 days before ovulation plus ovulation day itself. The 2-3 days before ovulation are your most fertile.
Understanding Your Results
Fertile Window
The 6-day period when conception is most likely to occur. This includes the 5 days before ovulation and ovulation day itself.
Peak Fertility
The 2-3 days leading up to ovulation offer the highest chance of conception. This is when you should prioritize having sex.
Timing Matters
Sperm can survive up to 5 days, but the egg only lives 12-24 hours after ovulation. Timing intercourse before ovulation is key.
Track Additional Signs
Combine this calculator with tracking cervical mucus, basal body temperature, and ovulation predictor kits for best results.
Learn More About Fertility
Complete Fertility Guide
Get comprehensive information about fertility timing, ovulation signs, and maximizing your chances of conception with our detailed guides.
Quick answer
This calculator estimates your most fertile days so you can time sex more effectively when trying to conceive. It is best used as guidance, not certainty. For better accuracy, pair date-based estimates with ovulation signs and cycle tracking.
What can change your result
- Ovulation day can shift from month to month.
- Sperm survival and cervical mucus quality matter.
- Regular logging improves confidence in timing.
When to get medical advice
- If you are under 35 and trying for 12 months without success.
- If you are 35+ and trying for 6 months without success.
- If cycles are very irregular or absent.