Free Tools
Mayan Gender Predictor
An ancient parity method: your age and the conception month decide boy or girl — instantly, and just for fun.
Want this in your pocket? Get the iOS app:
How this works
The Mayan gender predictor is a traditional method attributed to ancient Mayan numerology. It looks at exactly two numbers: the mother's age at conception and the month of conception. Instead of charts or calendars, it asks one simple question — are those two numbers both even, both odd, or mixed?
To use it, pick the mother's birth date and tap the month you conceived (or plan to conceive). The prediction updates instantly: if the age and the month are both even or both odd, the method says girl. If one is even and the other is odd, it says boy.
This tool is a 1:1 port of the Mayan predictor inside the ProbaBaby iOS app. Like the app, it anchors the conception date to the 15th of the chosen month in the current year — the year is not selectable, so the age used is your age as of the middle of that month this year.
This is for entertainment only and has no scientific basis. Because there are only two possible answers, a rule like this lands on the right one about as often as a coin flip — enjoy it as a fun tradition, not a diagnosis.
The math behind it
The engine builds a conception date fixed to day 15 of your chosen month: conceptionDate = (currentYear, chosenMonth, 15). The 15th stands in for "the middle of the month", and the year is always the current year — exactly like the app, which has no year input.
It then computes the mother's age as the number of full calendar years between her birth date and that anchored conception date. If the birth date somehow falls after the anchor, the age is clamped to 0 (and 0 counts as even).
The prediction is pure parity arithmetic: ageIsEven = age % 2 == 0 and monthIsEven = month % 2 == 0. If ageIsEven equals monthIsEven — both even or both odd — the result is girl ("Both Same"). If they differ — one even, one odd — the result is boy ("Both Different").
Because the year is silently fixed to the current year, picking January versus December can change the computed age (and therefore the prediction) if your birthday falls between those months. That is a quirk of the original app we deliberately preserved for parity.
There is no lookup table and no biology in this formula — it is a binary rule over two parities. Statistically, that is a coin flip: expect roughly 50% accuracy, which is exactly why this tool is labeled entertainment-only.
Frequently asked questions
It compares two parities: the mother's age at conception and the conception month (1–12). 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. That's the whole rule — no charts, no lookup tables.
The month's even/odd status is half of the rule. The engine anchors the conception date to the 15th of your chosen month — the "middle of the month" — and uses the month number (January = 1 through December = 12) to decide whether it counts as even or odd.
This tool is a 1:1 port of the ProbaBaby iOS app, where the conception year is fixed to the current year with no input. That means your age is computed as of the 15th of the chosen month this year — so choosing a month before or after your birthday can change the computed age and flip the prediction.
About as accurate as a coin flip — roughly 50%. It is for entertainment only and has no scientific basis. Treat it as a fun tradition to share, not a way to actually determine your baby's sex.
If the birth date falls after the anchored conception date (the 15th of the chosen month in the current year), the web version clamps the age to 0 for display, and 0 counts as even in the parity rule.
Both are legendary traditional methods, but they work differently: the Chinese method looks up a prediction in a chart based on age and month, while the Mayan method uses a single even/odd parity rule. Neither has scientific backing — try both and compare for fun.