Frequently Asked Questions

No. Independent studies put it at roughly 50 percent, which is what you would get by flipping a coin. It is a piece of folk tradition, not a diagnostic tool. For a real answer, an ultrasound from about 18 weeks or a NIPT blood test from about 10 weeks is what your doctor will use.

The chart is indexed by lunar age, which is typically one to two years higher than your Gregorian age. You do not need to work it out yourself: enter your real date of birth and the calculator converts it, including the jump that happens at Chinese New Year rather than on your birthday.

Enter the date you conceived, not your due date, though if you only know your due date, switch the toggle and the calculator will work backwards 266 days for you. The chart then uses the lunar month that date falls in, which rarely lines up with the Western month.

The Chinese calendar adds an extra intercalary month roughly every three years to stay in step with the solar year, so some years have thirteen months. If your conception date falls inside one, the calculator flags it and uses the base month number, because the traditional chart has no separate row for a leap month.

The chart was designed for single pregnancies and returns exactly one answer, so it cannot say anything meaningful about twins. You are welcome to try it for fun, but treat the result as a novelty.

The traditional account is that it was found in a Qing dynasty royal tomb and is around 300 years old. There is no verifiable documentary evidence for that origin story, and the version circulating online today is best understood as folk tradition rather than a historical artefact.

Yes. The full traditional chart covers lunar ages 18 to 45 and every row is implemented here, including 43, 44 and 45. Outside that range the chart simply has no data, and the calculator tells you so rather than guessing.

No. The entire calculation runs in your browser. Your dates are never sent to a server, logged, or saved.