A fun, centuries-old folklore tradition for guessing boy or girl, based on the mother's lunar age and the lunar month of conception.
The reliable ways are a mid-pregnancy anatomy ultrasound (usually 18–22 weeks), or earlier genetic tests like NIPT or CVS if you're having them for other reasons. Traditions like the lunar chart above, or old wives' tales, are fun but essentially a coin flip — the real odds of a boy or girl are close to 50/50 regardless of method.
No natural method has been scientifically proven to reliably choose a baby's sex — sex is determined by which sperm (X or Y) fertilizes the egg, essentially at random. Some folklore theories (like timing intercourse further from ovulation) claim to shift the odds slightly, but solid clinical evidence for this is lacking. If you're tracking your cycle for family planning generally, our Ovulation Tracker can help pinpoint your fertile window.
Same answer as for a girl, in reverse: there's no proven natural method to reliably select for a boy, since sex depends on random chance at fertilization. The only methods with real, scientifically demonstrated success rates involve clinical sperm-sorting combined with IVF, which are typically used for medical reasons rather than pure preference.
Folklore methods like the Chinese lunar calendar chart above are essentially a coin flip dressed up in tradition — fun to try, but not more accurate than guessing. A mid-pregnancy ultrasound is generally quite reliable (often 95%+ accurate) once the anatomy is clearly visible, and genetic blood tests can be even earlier and more precise.