Ovulation Calculator
Predict your ovulation date, fertile window, and most likely conception days.
Timing Your Fertile Window
Ovulation usually occurs 14 days before your next period — not after your last one. The 6-day fertile window (5 days before ovulation plus ovulation day) is when conception is possible. Peak fertility is the 2 days right before ovulation.
Boosting Accuracy
- Track 3+ cycles to find your average cycle length
- Use LH test strips around day 10–16 for precise ovulation detection
- Watch for cervical mucus changes (egg-white consistency = fertile)
- Record basal body temperature to confirm ovulation happened
Frequently Asked Questions
When does ovulation happen?
Typically 14 days before your next period starts, not 14 days after your last one began. For a 28-day cycle that lands on day 14; for a 32-day cycle, day 18.
How long is the fertile window?
About 6 days: the 5 days leading up to ovulation plus ovulation day itself. Sperm live up to 5 days; the egg survives around 24 hours.
Can I get pregnant outside the fertile window?
It's unlikely but possible if cycle length varies. Stress, illness, and travel can shift ovulation by several days.
Is this calculator accurate for irregular cycles?
No calendar method is reliable for cycles that vary by more than ±4 days. Consider ovulation predictor kits (LH tests) or basal body temperature tracking for better accuracy.