Plan Your Fertile Window
Track the fertile days around ovulation to optimize timing for conception. Enter the first day of your last menstrual period and your average cycle length.
Tally the number of days from one period's first day to the next when cycles are regular.
How to Use This Calculator
Track your cycles
Record the first day of your period and the number of days until the next period for several cycles to determine an average length.
Input cycle details
Enter your last menstrual period date and average cycle length. The calculator estimates ovulation as cycle length minus 14 days.
Plan intercourse accordingly
Intercourse every 1–2 days during the fertile window provides optimal chances. Continue tracking to fine-tune timing in future cycles.
Formula
Estimated ovulation date = LMP + (cycle length − 14) days
Fertile window = Ovulation − 5 days through Ovulation + 1 day
Implantation window = Ovulation + 6 to +10 days
Earliest reliable home pregnancy test = Ovulation + 10 days (after implantation). Missed period = LMP + cycle length
Full Description
Conception is most likely in the five days leading up to ovulation and on ovulation day itself. Sperm can survive up to five days in cervical mucus, while the ovum remains viable for about 24 hours after release. This calculator uses the standard method of subtracting 14 days from the cycle length to estimate ovulation. While convenient, actual ovulation may occur earlier or later, highlighting the importance of combining calendar tracking with physiological signs such as LH surges, cervical mucus changes, or basal body temperature shifts.
Frequently Asked Questions
What if my cycles are irregular?
Irregular cycles make prediction harder. Track multiple cycles, use ovulation tests, or consult a clinician for further evaluation.
Can stress or illness shift ovulation?
Yes. Stress, illness, or travel can delay ovulation, affecting fertile days and period timing.
How accurate is this method?
Calendar methods provide estimates. For higher accuracy, combine with ovulation predictor kits, cervical mucus monitoring, or ultrasound.
Should I keep tracking after I conceive?
Once pregnant, record the LMP to share with your provider. Ovulation date can refine due date estimates.