What the research found
A 2010 study by Eduardo Villamor and colleagues tested the Chinese lunar calendar method using 2,840,755 singleton births in Sweden between 1973 and 2006. The researchers found essentially no predictive agreement beyond chance.
Their conclusion was that it was no better than tossing a coin. Read the original study abstract on PubMed or the paper through DOI 10.1111/j.1365-3016.2010.01129.x.
What this means for your result: “Boy” or “Girl” here is the output of a traditional chart. It is not a diagnosis, a test result or an individualized probability.
A more recent study
A 2023 study at Koru Ankara Hospital in Turkey included 17,580 singleton births. It reported a kappa statistic of 0.002 and a p-value of 0.797, finding no meaningful agreement beyond chance between the calendar guesses and recorded sex at birth. Read the original paper in Actual Gynecology and Obstetrics.
This was a retrospective study from one hospital. It estimated conception by adding 14 days to the recorded last menstrual period; that approximation can introduce error. It does not validate every circulating chart or prove what will happen in an individual pregnancy. Together, the studies provide no support for a reliable prediction claim.
Can a Chinese gender predictor be 100% accurate?
No evidence supports a 100% accuracy claim for this traditional chart. A match with one pregnancy is not a guarantee for the next. A free calculator, a paid chart and a printable PDF have the same underlying limitation.
Why can it seem to work?
A chart with two result labels will sometimes match what later happens. One match does not show predictive power. Personal stories cannot tell us how often guesses failed or how the comparison was made.
Claims such as “90% accurate,” “scientifically proven” or “guaranteed” need strong evidence. We do not make those claims or attach a confidence score to a result.
Do lunar-date corrections make it reliable?
Using lunar age and lunar month makes the calculation consistent with its stated rules. It does not demonstrate that the rules predict biological outcomes. These are different questions:
- Calendar correctness: were dates converted and the table read consistently?
- Predictive validity: does the table predict the outcome better than chance?
We test the first and explain the evidence about the second. Inspect the full method and chart source.
Why did another website give a different answer?
Chart versions, regular versus lunar age, approximate conception dates and leap-month conventions can all affect a lookup. Treat disagreements as another reason to approach this as folklore, rather than trying repeatedly for a preferred answer.
For questions about your pregnancy
Use a qualified healthcare professional for decisions about pregnancy, screening and test interpretation. This website does not assess a pregnancy or recommend medical procedures. Do not use its results for health decisions or to plan a child’s sex.
The common search term “gender predictor” names this traditional tool. Its boy/girl guesses do not tell you a child’s future gender identity.
Research references
Villamor E, Dekker L, Svensson T, Cnattingius S. Accuracy of the Chinese lunar calendar method to predict a baby’s sex: a population-based study. Paediatric and Perinatal Epidemiology, 2010. PMID: 20618730.
Jafarzade A, Aghayeva S, Mungan TM, Biri A, Ekiz OU. Predicting Baby Gender Using the Chinese Lunar Calendar. Actual Gyn. 2023;15:57-60. Read the full paper (PDF).
This page has not been reviewed or endorsed by a medical professional.