Ovulation Calculator
Estimate your next ovulation day, 6-day fertile window and next period — from just your last period date and cycle length. Nothing leaves your device.
Find your fertile window
How the estimate works
Ovulation usually happens about 14 days before the next period — not 14 days after the last one, which is why cycle length matters. The fertile window spans roughly six days: the five days before ovulation (sperm survive up to five days) plus ovulation day itself (the egg lives about 24 hours). Calendar estimates work best for regular cycles; if yours varies a lot, ovulation test kits or temperature tracking are more reliable.
Signs of ovulation
Beyond the calendar estimate, your body gives clues: cervical mucus becomes clear and stretchy (like egg white), basal body temperature rises slightly after ovulation, and some women feel a mild one-sided twinge. Ovulation predictor kits detect the hormone surge a day or two before. Combining these signs with the calendar gives a more reliable picture than dates alone.
Trying to conceive vs spacing pregnancies
To improve the chance of conceiving, the most fertile days are the two to three days leading up to ovulation. If you are instead trying to avoid pregnancy, remember that calendar estimates are not a reliable contraceptive — sperm can survive up to five days and ovulation timing varies, so speak to a healthcare provider about proper family-planning methods.
Frequently asked questions
Can I get pregnant outside the fertile window?
It is less likely but possible, because ovulation timing varies and sperm can survive several days. Calendar methods are not reliable contraception.
How many days after my period do I ovulate?
For a 28-day cycle, ovulation is around day 14; for longer or shorter cycles it shifts, as it happens about 14 days before the next period.
Does a regular cycle guarantee I ovulate?
Usually, but not always. Some cycles are anovulatory. If you are tracking for conception and unsure, a doctor can confirm ovulation.
When do I ovulate?
About 14 days before your next period — day 14 of a 28-day cycle, day 18 of a 32-day cycle.
How long is the fertile window?
About 6 days: five days before ovulation plus ovulation day.
How accurate are ovulation calculators?
Good estimates for regular cycles; tests and temperature tracking are more precise.