Chinese Conception Calendar: How to Find Your Conception Date and Read the Chart

The chinese conception calendar is a square lookup table, traditionally attributed to a Qing-dynasty palace document, with the mother's lunar age running down one axis (most modern reproductions show ages 18 through 45) and the twelve Chinese lunar months running across the other. Each intersection cell is labeled either “B” for boy or “G” for girl, and the prediction comes from finding the cell that matches the mother's lunar age at the moment of conception and the lunar month in which conception happened.

The chart goes by many names in English — chinese gender chart, chinese birth chart, chinese pregnancy calendar, chinese baby calendar — but the underlying object is the same grid. The reason “conception calendar” is the most technically accurate name is that conception is the only date the original chart actually consumes. Due date and birth date are not in the lookup at all. Whenever you see a tool that asks for your due date or your baby's birth date, it's silently computing back to an estimated conception date before doing the lookup — sometimes well, sometimes badly.

In Chinese, the chart is most commonly called 清宫表 (qing gong biao, “Qing palace chart”) or 生男生女表 (sheng nan sheng nu biao, “boy or girl chart”). Neither Chinese name uses the word “birth” or “due date” — the chart was built inside a tradition where lunar conception month and lunar maternal age were the obvious two inputs to ask about. The English habit of phrasing it as a “birth” calendar is mostly a translation artifact.

Three different dates float around any pregnancy: the date of conception, the estimated due date, and the actual birth date. They can sit forty weeks apart, and they can fall on either side of a Chinese new year — which is the part that wrecks results. If you accidentally use the wrong one, you can land in a completely different row of the chart and read off the opposite prediction.

Consider a conception that happens in early February. Depending on the year, Chinese new year (the start of the lunar year) might fall a week before or a week after that conception. A few days' mistake in the date can move your lunar age up by a full year, because traditional Chinese age ticks over at lunar new year — not on a Western birthday. That single-row shift is the most common reason two people computing the “same” chart for the same person get different answers.

This is also why the conception-date-first approach is more faithful to the original chart than the due-date-first or birth-date-first approach. Due date is itself an estimate: it's typically calculated as the first day of the last menstrual period plus 280 days, and the actual conception date is roughly 266 days before birth. Working backward from a due date introduces a built-in two-week assumption about ovulation timing that doesn't hold for everyone. The American College of Obstetricians and Gynecologists notes that ovulation can vary by several days from cycle to cycle, so the “LMP + 14 days” rule is a useful approximation but not a hard rule.

If you came here from our chinese gender calendar by due date guide and want to compare answers, it's worth running the same pregnancy through both methods. The due-date method back-computes conception assuming a textbook cycle; the conception-date method here uses whichever signal you actually have (ultrasound, IVF transfer, or LMP). Disagreements between the two answers usually come from one being more accurate than the other about when conception actually happened.

There are four practical ways to estimate the conception date, ranked from least to most accurate. Use the highest-accuracy method you have data for.

1. From your last menstrual period (LMP). Take the first day of your last period before becoming pregnant and add roughly fourteen days. This places conception near the middle of a textbook 28-day cycle, which is when ovulation usually occurs. The result is an estimate, not a fact — cycles vary, ovulation slides, and a shorter or longer cycle will throw the number off by several days. This is the method most online calculators default to when no better data is provided.
2. From a first-trimester ultrasound. If you had an early dating scan (typically between week 8 and week 13), the technician will have written down an estimated gestational age based on the size of the embryo or fetus. Subtract that gestational age from the date of the scan to back-compute the LMP, then add fourteen days. First-trimester ultrasound is the most accurate dating tool available in a typical pregnancy and is usually within three to five days of the true conception date.
3. From a known intercourse window or ovulation test. If you were tracking fertility — using basal body temperature, cervical mucus observations, ovulation predictor kits, or a wearable fertility tracker — you may have a narrow window of one to three days when conception almost certainly occurred. Use the middle of that window. This is the most accurate non-IVF method, and one of the Mandarin students I taught a few years ago, who was doing fertility awareness for medical reasons, knew her conception date to the day for exactly this reason.
4. From an IVF transfer date. If your pregnancy started with in vitro fertilization, your clinic has the exact transfer date on file. For a 5-day blastocyst transfer, the conception date (more precisely, the fertilization date) is the transfer date minus five days. For a 3-day cleavage-stage transfer, subtract three days. This is the only method that gives you the conception date with no estimation at all.

Once you have a date, write it down in your local solar (Gregorian) calendar. The next step is converting that solar date into a Chinese lunar month, which is where most readers get tripped up. The good news is that the conversion is mechanical, not interpretive — once you know the rules, you can do it in under a minute. The National Institutes of Health publishes general fertility-awareness resources that explain ovulation timing in more depth, if you want to refine method 1 above into something closer to method 3.

The Chinese lunar calendar runs on twelve months tied to the cycles of the moon. Each lunar month begins on a new moon and lasts twenty-nine or thirty days. Lunar new year — the first day of the first lunar month — falls somewhere between late January and mid-February in the solar calendar, depending on the year. The lunar months do not line up cleanly with January through December, and that's the reason a conversion step exists at all.

To convert your solar conception date into a lunar month, the simplest approach is to look it up in a published conversion table. The official almanac maintained by the Hong Kong Observatory is the most authoritative free source — it gives the official lunar-to-solar mapping each year and is the same data Chinese newspapers and pocket calendars print. Any reputable Chinese lunar calendar app uses this dataset. Avoid sites that give a date without showing their source; the conversion has to handle leap months, and incorrect tools quietly get them wrong.

About leap months: in roughly seven out of every nineteen lunar years, the Chinese calendar inserts a thirteenth month called a leap month (闰月, run yue), which repeats the number of the preceding month — “leap fifth month” (闰五月) follows the regular fifth month. If your conception falls inside one of these leap months, the published convention used by almost every Chinese conception chart is to count the leap month under the same number as its parent — so leap fifth month conceptions look up the row for lunar month 5.

Once you have the lunar month number, do not forget to also convert your age. Your Chinese lunar age at the moment of conception is what the chart asks for, not your Western age. The short version is: count yourself as one year old at birth, then add a year each lunar new year. For most people this means lunar age equals Western age plus one or two. The full conversion has corner cases (especially for people born in January or early February), and our dedicated lunar age calculator handles them automatically. The deeper background on why this counting tradition exists is covered in our chinese pregnancy calendar guide.

Once you have the two inputs — lunar age at conception and lunar month of conception — reading the chart is mechanical. Find the row matching your lunar age along the left edge. Find the column matching your lunar conception month along the top edge. Trace your finger across and down. The cell where the row and column meet is your prediction: “B” for boy, “G” for girl. That's the entire algorithm.

A practical example. Suppose a friend tells you she is 29 in Western years, was born in June, and conceived on April 10, 2026. Her lunar age at conception, after adjusting for the lunar new year that already passed in February 2026, is 30. April 10, 2026 in the solar calendar falls inside lunar month 2 of the bing-wu year (the Year of the Horse). Her chart lookup is therefore: row 30, column 2 — and on the canonical Qing palace chart, that cell shows “B.” That's the full reading. There is no weighting, no aggregation, no secondary lookup.

A few common reading mistakes I had to walk students through repeatedly:

• Reading off the wrong row because Western age was used instead of lunar age. Always convert age first.
• Reading off the wrong column because solar (Gregorian) month was used instead of lunar month. January is not lunar month 1.
• Mixing up “G” and “B” in non-English reproductions of the chart, where “男” (nan, male) and “女” (nu, female) appear instead. If you're using a Chinese-language chart, double-check which character is which before you read your cell.
• Looking at the wrong axis entirely because some reproductions flip the chart so that age runs across the top and month runs down the side. Read the axis labels before you read the cell.

Step-by-step walkthroughs with a different worked example live in our how-to-use guide, and the underlying chart itself is on the Chinese Gender Calendar homepage for direct use.

You will see this exact grid called by half a dozen different names in English, and a question I got over and over from students was whether those names referred to different charts. They do not. The chinese conception calendar, chinese birth calendar, chinese pregnancy calendar, chinese gender chart, chinese baby gender predictor, and Qing palace chart all describe the same square lookup table.

The differences are framing, not data. A “conception calendar” emphasizes the date of conception as the input — useful when you know your conception date precisely from IVF or careful tracking. A “birth calendar” (especially in older Chinese-language usage of 生男生女表) emphasizes that the chart predicts the sex of a future birth. A “pregnancy calendar” emphasizes the phase of pregnancy you're in when consulting it. A “due date calculator” version asks for the due date and silently back-solves to a conception date before doing the lookup. Underneath all four wrappers the table is the same, and the answer depends on getting the lunar age and lunar conception month right.

This matters in practice when comparing answers across sites. If you run the same pregnancy through three different sites and get three different predictions, the issue is almost never that the sites are using different charts. The issue is almost always that they are using different assumptions to estimate conception date, different lunar age conversions, or a different convention for leap months. Pin those three things down and the answers will line up. The chart itself is fixed.

If you want to dig further into the cultural background, the differences between maternal lunar age and Western age, or the history of the Qing palace document, those are covered across the rest of our guides — along with the editorial note about who writes here on my author page.