Free Ovulation Calculator 2026 to predict your ovulation date and fertile window based on your menstrual cycle. Plan pregnancy with accurate fertility tracking.
Predict your ovulation date and fertile window to help plan or prevent pregnancy
This ovulation calculator estimates your most fertile days based on your menstrual cycle. Ovulation typically occurs about 14 days before your next period starts. Knowing when you ovulate can help you plan for pregnancy or understand your cycle better. For most accurate results, track your cycle for several months.
Ovulation timing is calculated based on your menstrual cycle length and luteal phase duration.
Ovulation Date = First Day of Last Period + (Cycle Length - Luteal Phase Length)
Fertile Window Start = Ovulation Date - 5 days
Fertile Window End = Ovulation Date + 1 day
Next Period Date = First Day of Last Period + Cycle Length
Current Cycle Day = Days Since Last Period + 1
Example with 28-day cycle and 14-day luteal phase:
Ovulation = Last Period + (28 - 14) = Day 14
Fertile Window = Day 9 to Day 15
Ovulation is typically calculated by subtracting the luteal phase length (usually 14 days) from your cycle length, then adding that number to the first day of your last period. For example, with a 28-day cycle and 14-day luteal phase: Ovulation = Last Period + (28 - 14) = 14 days after your period starts.
The fertile window is the 6-day period when pregnancy is possible. It includes the 5 days before ovulation and ovulation day itself. Sperm can survive in the female reproductive tract for up to 5 days, while the egg is viable for 12-24 hours after ovulation. The most fertile days are typically the 2-3 days right before ovulation.
The calculator provides an estimate based on average cycle patterns. Actual ovulation can vary by a few days each month due to stress, illness, or hormonal changes. For more precision, combine this calculator with ovulation predictor kits, basal body temperature tracking, or cervical mucus monitoring.
If your cycles are irregular, use the average length of your last 3-6 cycles for the most accurate estimate. Track your cycles for several months to identify patterns. If cycles vary by more than 7-9 days, consider consulting a healthcare provider as irregular cycles can affect ovulation timing.
The luteal phase is the time between ovulation and your next period. It typically lasts 12-16 days, with 14 days being average. This phase is relatively consistent for each individual, while the follicular phase (before ovulation) can vary. Knowing your luteal phase length improves ovulation prediction accuracy.
For the most accurate results, wait until at least the first day of your missed period (approximately 14 days after ovulation). Testing too early may result in a false negative. Early detection pregnancy tests can detect pregnancy 7-10 days after ovulation, but results are more reliable after your expected period date.
While this calculator can help you understand your fertile window, it should NOT be used as a sole method of birth control. Ovulation timing can be unpredictable, and sperm can survive for several days. If preventing pregnancy is your goal, consult a healthcare provider about reliable contraceptive methods.
The calculator automatically removes calculation history older than 3 days to keep your data current and relevant for tracking recent cycles. This feature helps maintain privacy and ensures you're working with recent cycle information. You can manually clear your history anytime using the 'Clear History' button.