1
Pregnancy & Baby
Chinese Gender Predictor — Boy or Girl by the Chinese Lunar Chart
How the ancient Chinese lunar calendar chart guesses Boy or Girl — and why it's really just a coin flip
The Chinese gender predictor is one of the oldest and most-shared baby games online — a grid that supposedly tells you whether you're carrying a boy or a girl. Legend says the chart was unearthed from a royal tomb near Beijing centuries ago; whatever its true origin, it works the same way it has on every pregnancy forum: you find your lunar age at conception down one side and the lunar month you conceived across the top, and the box where they meet reads either Boy or Girl.
This page implements the standard 18-to-49 lunar age by 1-to-12 lunar month chart that nearly every online version uses. Two quirks of the Chinese reckoning system are what make it feel mysterious:
- Lunar age is not your regular age. In the traditional Chinese count, a baby is considered 1 year old at birth (the time in the womb counts), and everyone clicks up a year at Lunar New Year rather than on their birthday. The everyday shortcut this calculator uses is lunar age ≈ Western age + 1, measured at the moment of conception — so a 29-year-old who conceives is read on the age-30 row.
- Lunar months don't line up with January–December. The Chinese New Year drifts between late January and mid-February, so a baby conceived in early February may still fall in the 12th lunar month of the previous year. A precise reading needs the conception date converted to the lunar calendar; this tool uses a practical approximation that lands on the right row and month for the overwhelming majority of dates.
Worked example. A mother turns 30 in Western years and conceives in July. Her lunar age reads as 31, the lunar month is roughly 6, and the classic chart returns Boy. Change the conception month to October (lunar month ~9) and the same age-31 row flips to Girl — which is exactly why the game is fun to play and exactly why you shouldn't repaint the nursery over it.
Is any of this real? No. Multiple studies — including a frequently cited analysis in the journal of the Canadian Medical Association — found the chart performs no better than chance, right roughly 50% of the time, the same odds as a coin flip. Sex is set at fertilization by whether the sperm carries an X or a Y chromosome, something a lunar grid cannot know. The only methods that actually reveal sex are medical: a mid-pregnancy anatomy ultrasound (around 18–20 weeks) or a cell-free DNA (NIPT) blood test as early as 9–10 weeks.
This calculator is a lighthearted tradition, not a diagnostic tool. Treat its answer as entertainment only — for an accurate result, ask your provider about ultrasound or NIPT. Nothing here is medical advice.
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Lunar age at conception ≈ Western age on the conception date + 1 • Lunar conception month ≈ the calendar month you conceived (adjusted toward the lunar calendar near Chinese New Year) • Prediction = the Boy/Girl cell of the traditional chart at [lunar age row 18–49] × [lunar month column 1–12] • Result is fixed by the chart, not by biology — accuracy ≈ 50% (chance)
📰 Formula
• Lunar age at conception ≈ Western age on the conception date + 1 • Lunar conception month ≈ the calendar month you conceived (adjusted toward the lunar calendar near Chinese New Year) • Prediction = the Boy/Girl cell of the traditional chart at [lunar age row 18–49] × [lunar month column 1–12] • Result is fixed by the chart, not by biology — accuracy ≈ 50% (chance)
🧪 Worked examples
2
Example 2
3
Example 3
4
Example 4
⚠️ Common mistakes
- Using your everyday (Western) age instead of the lunar age — the chart needs Western age + 1.
- Reading the calendar month directly when conception falls right around Chinese New Year, where the lunar month belongs to the previous year.
- Treating the result as a real prediction — it is correct only about half the time, no better than guessing.
- Mixing up conception month with your due-date month or LMP month; the chart wants the month you actually conceived.
- Assuming two different charts will always agree — minor lunar-conversion differences can flip a borderline cell.
💡 Tips
- Enter your date of birth and the month/year you conceived; the tool converts to lunar age and month for you.
- If you're not sure when you conceived, it's usually about two weeks after the first day of your last period.
- Play it twice — once with the conception month and once with the month either side — to see how easily the answer flips.
- For an answer you can actually trust, wait for the 18–20 week anatomy scan or ask about an NIPT blood test from 9–10 weeks.
- It's a great party game: have guests guess first, then reveal what the chart and the ultrasound each said.
Embed this calculator on your site
Copy the code below and paste it into the HTML of your site or blog.
<iframe src="https://www.calcnimbus.com/embed/chinese-gender-predictor-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How does the Chinese gender predictor chart work?
It cross-references the mother's lunar age at conception (down the side, ages 18 to 49) with the lunar month she conceived (across the top, months 1 to 12). The single cell where the row and column meet reads either Boy or Girl. It's a fixed lookup table, not a calculation based on any biology, so treat the answer as entertainment, not medical advice.
How accurate is the Chinese gender predictor?
About 50% — the same as flipping a coin. Studies, including a well-known analysis published by the Canadian Medical Association journal, found it does no better than chance. Because a baby's sex is set by the sperm's X or Y chromosome at fertilization, no lunar chart can actually predict it.
What is 'lunar age' and why is it my age plus one?
In the traditional Chinese system you're counted as 1 year old at birth, since time in the womb is included, and everyone ages up at Lunar New Year rather than on their birthday. The common shortcut is to add 1 to your Western age at conception. This tool does that adjustment for you from your date of birth.
Which month do I enter — conception or my last period?
Enter the month you actually conceived. If you only know your last menstrual period, conception is usually about two weeks later, so it may fall in the next month. Picking the wrong month can shift the chart's answer, since some rows alternate boy and girl month to month.
Why does the lunar month sometimes differ from the calendar month?
The Chinese New Year falls between late January and mid-February, so the lunar year starts later than January 1. A baby conceived in early February can still count as the 12th lunar month of the previous year. This calculator nudges the month toward the lunar calendar so borderline dates land correctly.
Can the Chinese chart tell me boy or girl better than an ultrasound?
No. An anatomy ultrasound around 18 to 20 weeks and a cell-free DNA (NIPT) blood test from about 9 to 10 weeks are the only reliable ways to learn a baby's sex. The Chinese chart is a centuries-old tradition you play for fun, with coin-flip odds.
Where did the Chinese gender chart come from?
Tradition says it was discovered in a royal tomb near Beijing and is hundreds of years old, though there's no verified historical record of its origin. What's certain is that it has spread worldwide as a popular pregnancy game. Its charm is its simplicity, not its accuracy.
Does the chart work for twins or IVF pregnancies?
The chart only ever returns a single Boy or Girl answer, so it has nothing meaningful to say about twins, and it can't account for IVF embryo selection. For any pregnancy, including twins or IVF, rely on your medical team's ultrasound or genetic testing rather than the chart.
Is it safe to make plans based on this prediction?
Only if you're prepared to be wrong half the time. Don't buy gender-specific gear, paint a nursery, or announce a sex based on the chart alone. It's a delightful party game, but it is not medical advice and not a substitute for an ultrasound or NIPT.