How to Calculate Ovulation Calculator
What is Ovulation Calculator?
An ovulation calculator estimates the fertile window based on the last menstrual period (LMP) and cycle length. Ovulation typically occurs 14 days before the next period (not 14 days after the LMP). The fertile window spans approximately 6 days — 5 days before ovulation plus ovulation day itself.
Step-by-Step Guide
- 1Ovulation day = LMP + (cycle length − 14)
- 2Fertile window = ovulation day − 5 through ovulation day + 1
- 3Sperm can survive in the reproductive tract for up to 5 days
- 4The egg is only viable for 12–24 hours after ovulation
Worked Examples
Input
LMP Jan 1, cycle length 28 days
Result
Ovulation Jan 15, fertile Jan 10–16
28 − 14 = day 14
Input
LMP Jan 1, cycle length 35 days
Result
Ovulation Jan 22, fertile Jan 17–23
35 − 14 = day 21