How Ovulation Is Calculated
Ovulation typically occurs 14 days before the next period starts. For a 28-day cycle, that's around day 14. The fertile window spans approximately 5 days before ovulation through 1 day after.
Ovulation Day = Cycle Length − 14
Signs of Ovulation
- Slight rise in basal body temperature (0.5-1°F)
- Change in cervical mucus (clear, stretchy, egg-white consistency)
- Mild pelvic pain (mittelschmerz)
- Positive ovulation predictor kit (OPK) test
Frequently Asked Questions
How accurate is this calculator? It provides estimates based on averages. Actual ovulation can vary by several days, especially with irregular cycles. Use with OPK tests for better accuracy.
How long is the fertile window? About 6 days: the 5 days before ovulation plus ovulation day itself. Sperm can survive up to 5 days, but the egg only 12-24 hours.
Can I get pregnant outside the fertile window? It's very unlikely but possible if your cycle is irregular or ovulation occurs earlier or later than predicted.