It was right for my first child. Does that count for anything?

Not on its own — a chart that says boy in 57 % of its cells will be right about half the time by chance, and every family that got a hit remembers it while the misses are forgotten. That is the mechanism that keeps these charts alive, and it is the same one behind lucky socks and successful horoscopes. Two hits in a row happen to about a quarter of families for no reason at all.

Why does the tool cover only lunar ages 18 to 45?

Because that is the extent of the chart as it circulates — twenty-eight rows and no more. Outside that range there is nothing to look up, and the tool says so rather than extrapolating a row that does not exist. Inventing cells would be the one thing worse than reproducing the ones there are.

What actually determines the answer?

Which of the father's sperm reaches the egg first — one carrying an X chromosome or one carrying a Y — decided at fertilisation and not influenced by anything either parent's calendar can record. It becomes visible on an ultrasound from about eighteen weeks, and a non-invasive blood test can read it earlier where it is offered. Those are the two ways to know, and this chart is not a third.

The Chinese Gender Chart Says Boy in 57 % of Its Cells

Published 9/17/2026 · 4 min read · Everyday calculators

Antonio Delgado — Traditions & pastimes writer at OneKitly

Symbolism · Calendars

Checked against 3 sources

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In short

The chart is a grid: twenty-eight rows for lunar ages 18 to 45, twelve columns for the lunar months of conception, and a B or a G in each of the 336 cells. Counting them gives 192 boy and 144 girl — 57.1 % against 42.9 %. That single fact settles most of what can be said about it. If the chart were consulted uniformly it would predict boy for 57 % of pregnancies, while the observed sex ratio at birth is close to 51 % boys worldwide, so the chart is biased by six points before any question of accuracy arises. There is no mechanism proposed and none found: the tool carries the chart because people look for it, prints the disclaimer beside the answer, and approximates the lunar age and month from your dates rather than applying the true lunar calendar — which it says on screen. An ultrasound at eighteen to twenty weeks is the answer to the question this chart is being asked.

336 cells, 192 of them boy and 144 girl. The chart is not even a fair coin, and the real ratio at birth is about 51 % boys — which is the whole measurement this article has to offer.

Lunar age is not your age

The rows are indexed by an East Asian reckoning in which a person is one year old at birth and gains a year at the lunar new year rather than on their birthday — so the same person can be counted as one or two years older than their Western age depending on where in the year they were born and when the chart is consulted. The columns are lunar months, which drift against the Gregorian calendar by up to a month and are corrected by an intercalary month roughly every three years. The tool approximates both from the dates you enter and says so; a chart consulted with a Western age and a Gregorian month is being read in the wrong row and the wrong column.

Where it comes from, as far as anyone can say

The usual account is that the chart was found in a Qing dynasty tomb near Beijing and is some seven hundred years old. The claim is repeated everywhere and sourced nowhere: there is no published excavation report, no catalogued object and no scholarly edition of the grid. That is worth stating as plainly as the count of cells, because the age is doing the persuading. What can be said without a source is that charts of this shape circulate widely in the Chinese-speaking world and have done for a long time, and that no version of them has ever been shown to track the outcome.

The 336 cells counted
What the chart says	Cells	Share
Boy	192	57.1 %
Girl	144	42.9 %
Observed at birth, worldwide	—	about 51 % boys

Frequently asked questions

It was right for my first child. Does that count for anything?: Not on its own — a chart that says boy in 57 % of its cells will be right about half the time by chance, and every family that got a hit remembers it while the misses are forgotten. That is the mechanism that keeps these charts alive, and it is the same one behind lucky socks and successful horoscopes. Two hits in a row happen to about a quarter of families for no reason at all.
Why does the tool cover only lunar ages 18 to 45?: Because that is the extent of the chart as it circulates — twenty-eight rows and no more. Outside that range there is nothing to look up, and the tool says so rather than extrapolating a row that does not exist. Inventing cells would be the one thing worse than reproducing the ones there are.
What actually determines the answer?: Which of the father's sperm reaches the egg first — one carrying an X chromosome or one carrying a Y — decided at fertilisation and not influenced by anything either parent's calendar can record. It becomes visible on an ultrasound from about eighteen weeks, and a non-invasive blood test can read it earlier where it is offered. Those are the two ways to know, and this chart is not a third.

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This chart is folklore with no scientific basis and no proposed mechanism. It is not a substitute for an ultrasound or for any advice from a midwife or doctor.

Sources

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