Chinese Gender Predictor Calculator

The Chinese gender chart is an old folk tradition that cross-references the mother’s age at conception with the month she conceived. Let’s be clear from the start: it’s just for fun, has no scientific basis, and doesn’t predict your baby’s actual sex. Enter the details below to see the guess.

It’s just for fun — and this has been measured

You don’t have to take our word for it. Researchers applied the published Chinese lunar calendar algorithm to 2,840,755 single births and compared each prediction with the baby’s actual sex. The agreement statistic came out at kappa 0.0002 — statistically indistinguishable from zero — and it didn’t improve for any group of mothers by age, education, body weight, or number of previous children. The authors’ own conclusion was that the method “is no better at predicting the sex of a baby than tossing a coin.”

That is exactly what you would expect from arithmetic alone. With only two possible answers, any chart, ring, or hunch is right about half the time. Being right 50% of the time is not evidence of anything.

What actually decides it: one chromosome

Sex is decided at fertilization, by chromosomes. The egg always carries an X chromosome; the sperm can carry X or Y:

• Sperm with X + egg with X = girl (XX)
• Sperm with Y + egg with X = boy (XY)

In other words, it’s the sperm that determines the sex, and it happens at the moment of conception — nothing to do with the month or the mother’s age.

How to find out the real sex

Reliable methods are medical tests:

• Prenatal cell-free DNA screening, a maternal blood test that MedlinePlus says can be done as early as the 10th week of pregnancy. It reads the fetal sex chromosomes along with the trisomy screen. It is a screening test: a positive result for a chromosome condition needs confirmation by amniocentesis or CVS.
• Ultrasound. MedlinePlus lists the baby’s sex among the things a second- or third-trimester scan can sometimes show — it does not publish a week from which the reading becomes reliable, so we don’t either.

Your doctor performs and interprets these during prenatal care. In the meantime, you can track the pregnancy with the conception date calculator and estimate your fertile window with the fertile window calculator.

This content is for information and entertainment only. To track your pregnancy and find out your baby’s sex, follow prenatal care with your doctor.