Ovulation Calculator
Find your most fertile days and ovulation date based on your cycle. Track your fertile window to maximize your chances of conception.
Enter Your Cycle Details
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Discover Your Fertile Days
Enter your cycle details on the left to calculate your ovulation date and fertile window.
How the Ovulation Calculator Works
Based on the luteal phase method — the most widely used approach in reproductive medicine
Luteal Phase Method
Ovulation is estimated by subtracting 14 days from your expected next period (cycle length − 14). The luteal phase — from ovulation to menstruation — is nearly constant at 14 days regardless of cycle length, making this a reliable baseline.
The Fertile Window
The fertile window spans 6 days: 5 days before ovulation and ovulation day itself. Sperm can survive up to 5 days in the reproductive tract, meaning sex in the days before ovulation is just as important as on ovulation day.
Cycle Length Matters
Longer cycles push ovulation later, not earlier. A 35-day cycle ovulates around day 21; a 21-day cycle around day 7. Our calculator adjusts automatically — just enter your average cycle length for accurate results.
Physical Signs of Ovulation
Combine calculator predictions with these body signals for the most accurate fertility tracking
Basal Body Temperature Rise
Your resting temperature rises slightly (0.2°C / 0.4°F) after ovulation and stays elevated until your next period. Chart it daily first thing in the morning for the most accurate picture.
Cervical Mucus Changes
In the days approaching ovulation, vaginal discharge becomes clear, slippery, and stretchy — like raw egg whites. This is your body's way of helping sperm travel to the egg.
LH Surge (OPK Positive)
A surge in luteinizing hormone (LH) triggers ovulation 24–36 hours later. Over-the-counter LH test strips (OPKs) detect this surge, giving you advance notice of your most fertile time.
Mittelschmerz (Ovulation Pain)
About 20% of women experience a brief, one-sided pelvic ache or twinge when the egg is released from the follicle. It typically lasts a few minutes to a few hours.
Cervical Position Changes
Around ovulation, the cervix rises higher, softens, and opens slightly. This can be monitored by self-examination, though it takes a few cycles to learn your own pattern.
Increased Libido
Many women notice heightened sexual desire around ovulation — an evolutionary adaptation designed to promote reproduction at the most fertile time in the cycle.
Understanding Your Menstrual Cycle
A typical menstrual cycle lasts 21–45 days, with 28 days being the average. The cycle begins on the first day of menstruation and ends the day before the next period starts. Ovulation — the release of a mature egg from the ovary — occurs once per cycle and marks the transition between the follicular phase and the luteal phase.
Ovulation prediction is based on the regularity of the luteal phase. Unlike the follicular phase (which can vary widely between women and even between cycles), the luteal phase is consistently 12–16 days, averaging 14 days. This means that knowing your cycle length gives us a reliable estimate of when ovulation occurs.
For women trying to conceive, timing intercourse to the fertile window can significantly improve monthly success rates. If you have already confirmed pregnancy, use our EDD calculator to find your estimated due date, and our week-by-week guide to follow your baby's development.
Ovulation Calculator — FAQs
Answers to common questions