Ovulation & Fertile Window
Calculator
Find your most fertile days, ovulation date, when to take a pregnancy test — and your due date if you conceive this cycle.
First day of last period
Cycle length
Period length
Free, instant — no sign-up needed for the result.
How it works
Ovulation happens roughly 14 days before your next period. We take your last period date and cycle length, project your next cycles, and mark the 6-day fertile window — the 5 days before ovulation plus ovulation day, when conception is possible.
We also show your implantation window (6–10 days after ovulation) and the earliest date a home pregnancy test becomes reliable — the day your next period is due.
Frequently asked questions
When do I ovulate?
Ovulation usually happens about 14 days before your next period starts — not 14 days after the last one. That's why your cycle length matters: in a 32-day cycle, ovulation is around day 18, not day 14.
What is the fertile window?
The 6 best days for conception: the 5 days before ovulation plus ovulation day itself. Sperm can survive up to 5 days, while the egg lives about 12–24 hours after release.
How accurate is the calendar method?
It's a good starting estimate for regular cycles, but ovulation can shift with stress, illness or travel. Ovulation predictor kits (OPKs) and basal body temperature tracking are more precise.
What if my cycles are irregular?
With irregular cycles (common with PCOS or thyroid issues), calendar predictions are unreliable. Track a few cycles, use OPKs, and consider talking to a doctor.
This is a calendar-based estimate for awareness — not medical advice and not a contraception method.