Chinese Gender Chart from Due Date (Lunar Age Predictor)

A Chinese gender calendar and gender predictor for when you know your due date and birthday but not the day you conceived.

It backs out the conception month, works out your lunar age, reads the traditional chart, flags borderline results, and explains why the chart is only about 50% accurate.

Last updatedHow we build & check our tools
Results will appear here once you enter your values.

The Chinese gender calendar is a coin flip: what the evidence says

The Chinese gender calendar, also sold as a Chinese gender predictor, is a table that pairs a mother's age with the month of conception and prints Boy or Girl in each cell. Stories say it was found in a royal tomb near Beijing about 700 years ago. No original document has been produced, and no study has shown that it works.

The best test of it is a 2010 study by Villamor and colleagues in Paediatric and Perinatal Epidemiology, which compared what the chart predicted against the actual sex of about 2.8 million babies born in Sweden between 1973 and 2006. The match rate was about 50%, no better than guessing, and it stayed at chance for every maternal age and year studied. That result is what you would expect from the biology.

  • What decides sex: an egg always carries an X chromosome. The sperm that fertilizes it carries either an X (girl) or a Y (boy). That is settled at fertilization and nothing about the mother's age or the lunar month changes the odds.
  • Why it feels right: with two outcomes about equally likely, any chart is right about half the time, and people remember the hits and forget the misses. About 105 boys are born for every 100 girls, so even always guessing Boy would be right slightly more than half the time.
  • What to do with it: treat it like a horoscope for baby-name chat. Do not paint a nursery, buy clothes, or tell relatives on the strength of it.

That is why this tool shows an entertainment-only banner above the result and again in the accuracy panel, instead of burying the caveat in a footer.

How this tool turns a due date and a birthday into a chart cell

Most Chinese gender calendars ask for the lunar month you conceived in, which is exactly what most people do not know. This tool works from the two dates you do have.

  1. Back out conception. Due date minus 266 days. Pregnancy is dated as 280 days from the last period, and conception is about 14 days into that, so 280 minus 14 is 266. This is the same arithmetic as Naegele's rule that the due date calculator uses, run in reverse.
  2. Convert to the Chinese lunar calendar. The lunar calendar follows the moon. Each month starts at a new moon and lasts 29 or 30 days, and about every third year adds a leap month so the calendar stays in step with the seasons. The tool holds the month lengths of every lunar year from 1900 to 2049 and counts the days from lunar new year, so it works offline and always gives the same answer.
  3. Work out lunar age. Born counts as 1, and each lunar new year adds one. The tool converts both your birth date and the conception date to lunar years, and the difference plus one is your lunar age at conception.
  4. Read the chart. The row is your lunar age (18 to 45) and the column is the lunar month (1 to 12). The cell says Boy or Girl, and the result shows the exact age and month so you can check it against any printed copy.
  5. Check how fragile it is. The tool repeats the lookup 14 days earlier and 14 days later. If either gives the other sex, the result is marked borderline.

Worked example: a mother born 15 June 1995 with a due date of 1 December 2025. Conception is estimated at 10 March 2025, in lunar year 2025 (which began 29 January 2025). Her birth was in lunar year 1995, so her lunar age at conception is 2025 minus 1995 plus 1, which is 31. 10 March 2025 is day 11 of the second lunar month (which began 28 February 2025), and the chart cell for age 31, month 2 reads Girl. Fourteen days earlier, 24 February, is still in month 1, where the age-31 row reads Boy, so this example is a borderline result.

Several versions of the chart circulate and they disagree in places. This tool uses the widely shared version published by immihelp.com, for example lunar age 21 reads Boy in month 1 and Girl in months 2 to 12. The same caution applies to every version: none has been shown to predict sex.

When you can find out the real answer

If you want to know rather than guess, these are the options, in the order they usually arrive. All are done through your prenatal care provider.

  • Cell-free DNA screening (NIPT), from about week 10. A blood sample from the mother contains fragments of the baby's DNA. The lab can see whether Y chromosome material is present. It is offered mainly to screen for chromosome conditions such as Down syndrome, and the sex result comes with it. It is a screening test with high, not perfect, accuracy.
  • Mid-pregnancy anatomy ultrasound, about weeks 18 to 22. The sonographer checks the baby's growth and organs, and can often see the genitals. The baby's position, and the sonographer's confidence, decide whether a clear answer is possible. See the due date calculator to place weeks 18 to 22 on your calendar.
  • Amniocentesis or chorionic villus sampling. These give a definite result but carry a small risk, so they are offered for medical reasons, not to learn the sex.
  • Birth. The one test that is always right.

Sex is not the only thing worth counting down to. The infant growth percentile calculator is useful after the birth, and the pregnancy weight gain calculator helps during it.

Related pregnancy tools and where this one fits

The Chinese gender chart answers one narrow question. These tools answer the practical ones.

Sources: Villamor E, Dekker L, Svensson T, Cnattingius S, 2010, Paediatric and Perinatal Epidemiology 24(4):398-400 (accuracy of the Chinese lunar calendar method); American College of Obstetricians and Gynecologists, Methods for Estimating the Due Date, Committee Opinion 700 (280-day pregnancy dating); ACOG on cell-free DNA screening (NIPT) and prenatal genetic screening; Hong Kong Observatory, Gregorian-Lunar Calendar Conversion Tables (lunar month lengths).

This tool is for entertainment and is not medical advice. Talk to your doctor or midwife about prenatal care.

Frequently Asked Questions

Common questions about the Chinese Gender Chart from Due Date (Lunar Age Predictor)

About 50%, which is the same as flipping a coin. Villamor and colleagues tested the chart in 2010 (Paediatric and Perinatal Epidemiology) against about 2.8 million Swedish births from 1973 to 2006 and found it no better than chance at telling boys from girls. Roughly half of all people who try it get a match, and that half then tells their friends it worked. This tool shows the chart reading because people search for it, and labels it as entertainment above the result for the same reason.

Sources & References

Villamor et al., Paediatric and Perinatal Epidemiology 24(4):398-400

Test of the Chinese lunar calendar method on Swedish birth records.
- About 2.8 million singleton births, 1973-2006.
- Agreement with the actual sex was at chance (kappa 0.0002), for every maternal age and year.
→Source: Paediatric and Perinatal Epidemiology(2010)

Chinese lunar calendar gender prediction chart

The traditional chart this tool reads.
- Rows are the mother's lunar age 18 to 45, columns are lunar months 1 to 12.
- Several versions circulate; this tool follows this published one cell for cell.
→Source: immihelp.com(2026)

Gregorian-Lunar Calendar Conversion Tables

Lunar month lengths and leap months used to convert dates.
- Lunar new year and month starts for every year the tool covers.
→Source: Hong Kong Observatory(2026)

Methods for Estimating the Due Date (Committee Opinion 700)

Due date is 280 days after the first day of the last menstrual period.
- Conception is about 14 days into that, so about 266 days before the due date.
→Source: American College of Obstetricians and Gynecologists(2017)

Explore More Tools

Explore these related tools for your next step.

health

Heart Rate Zone Calculator

Calculate target exercise heart rate zones from age, resting heart rate, optional measured max heart rate, and training method.

Try it now
health

Meal Log Pattern Classifier

Paste a meal log and an AI model in your browser lists meals and times and labels the pattern. No calorie counts. Private. Not medical advice.

Try it now
health

Workout Note Intensity Labeler

Paste a workout note and an AI model in your browser labels it Easy to Very hard from how you described it. Free, private. Not medical advice.

Try it now
health

Sleep Journal Signal Checker

Paste a sleep journal and an AI model in your browser lists bed and wake times, habits and patterns that show up together. Private. Not medical advice.

Try it now
health

Symptom Note Organizer

Organize symptom notes into timing, triggers and changes to bring to a clinician. AI model runs in your browser, nothing is uploaded. Not medical advice.

Try it now
health

Hydration Habit Note Analyzer

Paste notes on what you drank and an AI model in your browser lists drinks, timing and patterns to track. Free, private. Not medical advice.

Try it now