Lunar Month of Conception: How to Find Yours

Very few people know the exact day. That is fine; you need a good estimate, and the right estimate depends on what you do know.

• From your last period. The American College of Obstetricians and Gynecologists notes that in an average 28-day cycle, ovulation happens about 14 days before the next period starts. For a 28-day cycle that is about 14 days after the first day of your last period, which is what our calculator assumes when you choose the LMP option. If your cycles are longer, ovulation comes later: count back 14 days from when your next period would have started.
• From an ovulation test or tracking. Use the day of ovulation. A large study of couples trying to conceive found that conception followed intercourse only within a six-day window ending on the day of ovulation (Wilcox et al., 1995), so the ovulation day is the best single date to use.
• From a due date. Work backwards to the conception estimate your clinic gave you, or use our guide to the Chinese gender calendar by due date.
• From IVF. Most families use the transfer date or the retrieval date. There is no traditional rule for IVF, because the chart predates it; our IVF guide discusses the choice.

The lunar year changes at Chinese New Year, which falls between late January and late February. Any conception before that date belongs to the previous lunar year and is read from that year's twelfth (or eleventh) month. This trips people up every January.

Take January 30. In 2026 it is lunar month 12 of the 2025 year, because Chinese New Year 2026 was on February 17. In 2028 the same date is lunar month 1 of 2028, because Chinese New Year 2028 is on January 26. Same date, different lunar year, different column on the chart. The same New Year date also decides the mother's lunar age, which is why our Chinese New Year 2027 guide matters for anyone conceiving in early 2027.

These are the lunar months of the 2026 and 2027 lunar years. Neither year has a leap month. Every date comes from the Hong Kong Observatory conversion tables.

Source: Hong Kong Observatory tables T2026e, T2027e and T2028e, read October 15, 2026. For 2025, which has a leap sixth month, see our 2025 page; for 2028, which has a leap fifth month, see the 2028 chart page.

If you only know the Western month of conception, this shows which two lunar months it straddles in 2026 and which one covers more of its days. We counted it day by day from the table above. It is a guide for curiosity; for the chart, use the exact date.

Two patterns stand out. In 2026 the lunar month number usually runs one or two behind the Western month, because the lunar year started late, on February 17. And January and early February 2026 do not belong to lunar 2026 at all: they are the last two months of the 2025 Snake year. That one fact explains most of the January confusion we see.

Known date. You know you conceived on June 14, 2026. That is the last day of lunar month 4 (May 17 to June 14). The next day would have been month 5, so this is one of the boundary cases discussed below.

Last period, 28-day cycle. Your last period began on November 20, 2026. Adding 14 days gives an estimated conception on December 4, 2026, which falls in lunar month 10 (November 9 to December 8).

January conception. You conceived on January 20, 2027. Chinese New Year 2027 is not until February 6, so this is lunar 2026, month 12 (January 8 to February 5, 2027). Use your lunar age for lunar 2026, not 2027.

Here is the part most guides skip. A conception date estimated from a period is rarely exact to the day, and lunar months change every 29 or 30 days. We counted the 2026 lunar year against the table above: 80 of its 354 days, about one day in four, sit within three days of a change of lunar month. If your estimated date is one of them, the true conception may well have been in the neighbouring month.

The honest way to handle it is to read both columns. If they agree, you have your answer. If they disagree, the chart cannot tell you which one applies, because your input is not precise enough. Many parents in that position simply take the result of the month their best estimate falls in, and treat the other as the coin landing the other way.

Leap months create a bigger version of the same problem. The chart has twelve columns, so a leap month has to borrow one. This site reads a leap month as the month it repeats, which is the most common convention. Some websites skip the leap month entirely, which shifts every later month by one, and that is one of the main reasons calculators give different results for the same dates.

• Using the Western month number. March is not lunar month 3. In 2026 most of March is lunar month 1.
• Putting January in the new lunar year. Until Chinese New Year, you are still in the previous lunar year's last months.
• Entering the last-period date as the conception date. The two are about two weeks apart in a 28-day cycle, which is half a lunar month.
• Using the due date. A due date is roughly nine months after conception and says nothing about the lunar month you conceived in until you work backwards.
• Ignoring a leap month. In 2025 and 2028, a tool that skips the leap month gives you the wrong column for every later month of the year.

The lunar month is the column. The mother's lunar age is the row. Where they meet is the prediction. Our guide on how to read the Chinese gender calendar shows the grid, and the lunar age of the mother guide covers the row. Or let the calculator on the homepage do both conversions from your two dates.

Keep the result in proportion. When researchers applied this exact method, lunar month and lunar age, to 2,840,755 Swedish births, the chart matched the baby's sex no better than chance (Villamor et al., 2010). Getting the lunar month right makes your reading faithful to the tradition. It does not make it a medical test; the anatomy scan and NIPT are those.