Ovulation Calculator
Enter the first day of your last period and your usual cycle length. The calculator shows your fertile window, your most likely ovulation day, and the earliest date a pregnancy test is reliable.
How the calculator works
Ovulation happens about 14 days before the next period starts, not 14 days after the last one, which is why cycle length matters. The egg lives about 24 hours, but sperm survive up to five days, so the fertile window runs from five days before ovulation to the day after it. Couples who time intimacy inside that window every cycle have the best monthly odds of conceiving.
A calendar estimate is a starting point, not a guarantee. If your cycles swing by more than a few days, pair the dates with your body's own signals, cervical mucus and ovulation pain, explained in our ovulation signs guide. Cycles that are unpredictable month to month are worth reading about in our irregular periods guide, since conditions like PCOS shift ovulation or stop it entirely.
Trying to conceive?
Timing is half the work; the other half is the three months of preparation both partners bring to the fertile window. Our trying-to-conceive guide covers the habits with real evidence, folic acid before conception is the non-negotiable (see the folic acid guide), and the Trying-to-Conceive Couple's Pack covers both of you in one order, delivered anywhere in Pakistan with cash on delivery.
Already pregnant? The Due Date Finder shows your due date, your current week and your scan dates. More like this on the Quick Answers page.
Common questions
When do I ovulate after my period?
About 14 days before your NEXT period starts. On a 28-day cycle that is around day 14; on a 35-day cycle it is around day 21. That is why the calculator asks for your cycle length.
How long does the fertile window last?
About six days: the five days before ovulation plus the day of ovulation itself, because sperm survive up to five days while the egg lives about 24 hours.
Can I use this as a safe-days calculator to avoid pregnancy?
No. Cycle timing shifts too easily for calendar maths to be reliable contraception; a stressful month can move ovulation by days. Use it for trying to conceive, and use proper contraception to prevent pregnancy.
This tool provides general estimates for education and does not replace medical advice; the NHS guide to trying for a baby is a good clinical reference. If you have been trying for over a year (or six months past age 35), our infertility guide explains when and where to get help.