He Hun (合婚) is the traditional Chinese practice of comparing two birth charts before a marriage. It is the source of most modern BaZi compatibility readings, and it comes with a reputation — some of it earned, and some of it attached by popular retellings. This page explains what the practice actually examined, what a modern couple can still take from it, and where its limits are.
Historically, a family would commission a reading before a marriage was agreed, comparing the two charts the way you might compare two household inventories before joining them. The exercise was practical in intent. Four dimensions were usually examined.
Notice that none of those four is a yes-or-no test. They are comparisons. The traditional output was a description of the pairing, delivered to families who then decided what to do with it. The authority sat with the people, not with the chart. For the working version of the same four dimensions, see our compatibility overview, which follows the same structure.
Stripped of the wedding-planning pressure, He Hun is a fairly good tool for starting a conversation about difference. It gives two people a shared vocabulary for the places where they operate differently — one supplies the energy, the other supplies the structure, one needs more room than the other — without either having to be the one who raised it as a complaint.
Used that way, a comparison is a map. It marks where the road is easy and where it narrows. What it cannot do is drive. That distinction is the whole of this page.
The other thing worth keeping is the zodiac layer, which is genuinely charming and genuinely limited. Our guide to Chinese zodiac compatibility covers the harmonies and clashes in full, along with a reminder that the animal sign is one of the eight characters in a chart.
This is the part popular retellings skip, so it is worth stating plainly.
A comparison can tell you where two charts supply each other and where they rub. That is a real and usable output. It is also the entire output.
Some couples run a comparison while deciding whether to marry. If that is your case, the order matters. Use it to surface questions you have not asked yet, not to settle a question you have already answered. If a chart reading is the deciding vote in a marriage decision, the reading is being asked to do something it was never designed to do.
Our own comparison tool is built along the four traditional dimensions, with a written section on where the charts align and where they need attention. You can start with both birth dates — and if the birth time is uncertain, noon works. To see each chart on its own first, run the free BaZi calculator.
Run a comparison along the same four traditional dimensions.
Run a free compatibility match → Free to start · No sign-up · Or chart both people with the free BaZi calculator