Baby gender predictor by date

How the Chinese gender calendar works

The Chinese gender calendar is a centuries-old chart that cross-references the mother's lunar age at conception with the lunar month she conceived in, returning “boy” or “girl” from a fixed lookup table. Tradition holds that a copy was buried in a Beijing tomb roughly 700 years ago, though the actual provenance is debated by historians.

In practice, the calendar performs at chance level — about 50% accurate, the same as flipping a coin. The version on this page uses the standard 28×12 table that appears across virtually every English-language Chinese calendar tool, with the simplifying assumption that lunar age is roughly the mother's age plus one. It's a tradition many parents enjoy trying, not a prediction to plan around.

The Mayan method explained

The Mayan method is the simplest of the three: take the mother's age at conception and the year of conception. If both numbers are even, or both are odd, the prediction is girl. If one is even and the other is odd, the prediction is boy.

Like the Chinese calendar, this is folklore — by definition, parity-based prediction can't do better than chance because biological sex isn't correlated with calendar parity. People enjoy the method partly because it's easy to remember and partly because the result often disagrees with the Chinese calendar, giving you two predictions to talk about.

Predicting from parent traits

The third method asks five quick questions about pregnancy symptoms — cravings, morning-sickness severity, how you're carrying, mood intensity, and skin changes — and aggregates them into a soft probabilistic guess. Each question is rooted in old wives' tales: sweet cravings traditionally suggest a girl, salty cravings suggest a boy, severe morning sickness leans girl, and so on.

A few of these signals (notably morning-sickness severity) have shown a faint statistical association with biological sex in real-world studies, but the overlap is huge and they're not reliable for any individual pregnancy. We cap the “confidence” result at 90% no matter how lopsided your answers are, because the underlying signal genuinely isn't that strong.

How accurate are gender prediction methods?

The honest answer: traditional methods perform at roughly chance level. The only reliable ways to determine biological sex during pregnancy are medical:

• NIPT (non-invasive prenatal testing) — a blood draw from the mother that detects fetal DNA. Reliable from about 9–10 weeks of gestation onward; over 99% accurate for sex when enough fetal DNA is present.
• Mid-pregnancy anatomy ultrasound — typically between 18 and 22 weeks. Very accurate when the baby cooperates and a clear view is available.
• Amniocentesis or chorionic villus sampling (CVS) — definitive, but only offered when there's a medical reason because both carry a small miscarriage risk.

If knowing your baby's sex matters, talk with your healthcare provider about which medical option is appropriate for your pregnancy and timeline.

When can I find out my baby's gender medically?

The earliest reliable answer comes from NIPT at 9–10 weeks. Most practices run NIPT primarily as a chromosomal screening; sex determination is offered as part of the same report if you opt in.

If you're not having NIPT, the anatomy scan between 18 and 22 weeks is the most common moment parents find out. Sonographers can often see external genitalia clearly by then, though the baby's position can sometimes prevent a confident call. If that happens, a follow-up scan usually clears it up.

Frequently asked questions

Sources and further reading

• ACOG — Prenatal genetic screening tests (covers NIPT)
• Mayo Clinic — Noninvasive prenatal testing overview
• Wikipedia — Chinese gender predictor chart (history and cultural context)