Ovulation Calculator
Estimates ovulation by subtracting 14 from cycle length. Fertile window: 5 days before through 1 day after ovulation.
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How It Works
Estimates ovulation by subtracting 14 from cycle length. Fertile window: 5 days before through 1 day after ovulation.
Quick Reference
28-day cycle
Day 28 - 14
Ovulation day 14
35-day cycle
Day 35 - 14
Ovulation day 21
21-day cycle
Day 21 - 14
Ovulation day 7
Tips & Shortcuts
OPK test detects LH surge 12-36 hours before ovulation.
BBT rises 0.2C after ovulation confirming it occurred.
Common Mistakes
Assuming ovulation always day 14
Ovulation is 14 days BEFORE next period. 35-day cycle = day 21.
Relying solely on calendar for contraception
Calendar method has 9-25% failure rate.
Frequently Asked Questions
Ovulation typically occurs around day 14 — 14 days before your next period. Your fertile window spans approximately days 9–15.
The egg is viable for only 12–24 hours. Your fertile window is longer because sperm survive 3–5 days waiting for ovulation.
Common signs: mid-cycle pelvic pain, egg-white cervical mucus, a slight rise in basal body temperature (0.2–0.5°C), and a positive LH surge on an ovulation test strip.
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