This calculator estimates your ovulation day by working back from your next expected period: for most people, ovulation happens about 14 days before the next period starts. So it adds your cycle length to the first day of your last period, then subtracts 14 days. It's an estimate — real ovulation shifts from cycle to cycle, and irregular cycles vary the most. Ovulation predictor kits and cycle tracking give a more personal read.
The fertile window is the roughly six days that end on ovulation — the five days before, plus ovulation day itself — because sperm can survive for several days while the egg lasts about a day. The two days right before and including ovulation are the most fertile. If you're trying to conceive, those are the days to focus on; if you're avoiding pregnancy, this tool is an estimate only and not a form of birth control.
If this cycle turns into a pregnancy, most parents learn the baby's sex at the anatomy scan around 18–20 weeks — the natural moment to plan a party. When you're ready, Revealcast makes the reveal itself easy: guests guess pink or blue from one link and the answer plays on the big screen for everyone, including family who can't be there. Estimate the arrival with our due date calculator, or get inspired by these virtual gender reveal ideas.
Ovulation typically happens about 14 days before your next period starts. This calculator adds your average cycle length to the first day of your last period to estimate the next period, then counts back 14 days to estimate ovulation. Your fertile window is the five days before that day plus ovulation day itself.
It's an estimate, not a guarantee. The math assumes a fairly regular cycle, so the more your cycle length varies month to month, the less precise the prediction. If your cycles are irregular, ovulation predictor kits, basal body temperature tracking, or advice from your provider will give a more reliable picture.
A NIPT blood test can indicate the baby's sex from about 10 weeks, and the anatomy-scan ultrasound at roughly 18–20 weeks confirms it. That's why most gender reveal parties happen between about 18 and 24 weeks — late enough to know for sure and a natural time to celebrate.