Birthday Compatibility

How does birthday compatibility work?

Birthday compatibility here reads three classic systems from the same two dates of birth and blends them into one score. Enter both birthdays; everything is worked out in your browser, and only the results — a star sign, a zodiac animal and a number for each person — go into the link you share. Your dates themselves never leave your device.

First, the star sign comes from the month and day using the usual date ranges, and the two signs are scored by element the same way as our Zodiac Match: the same element starts at 88, fire with air at 84, earth with water at 83, with lower starts for the elements that pull apart and a small nudge by distance. Second, the zodiac animal comes from the year, but the year turns at Seollal rather than on January 1, so a January or February birthday may belong to the previous animal; we check every date against a table of Seollal dates from 1920 to 2040. The animals are scored as in our Chinese Zodiac Match: trines 92, secret friends 86, clashes 42. Third, the life path number adds up the digits of the year, month and day, and is scored as in our Life Path Compatibility, from 56 to 92.

The final score is 40% star signs, 30% zodiac animals and 30% life path numbers, rounded. We give the star sign a little more weight because it is the system most people already know. A system “approves” when its own score is 70 or more, so the card can say whether one, two or all three agree. To show how rare your result is, we compare it with every combination of sign pairs, animal pairs and number pairs — 78 × 78 × 78, or 474,552 — and report whether it sits in the top or bottom part of that spread.

A worked example: someone born on Jul 4, 1990 is Cancer · Horse · 3, and someone born on Nov 3, 1992 is Scorpio · Monkey · 8. Their star signs score 87%, their zodiac animals 60% and their life path numbers 72%. Weighted, that is 87 × 0.4 + 60 × 0.3 + 72 × 0.3 = 74.4, so the card shows 74%. 2 of 3 systems approve. The stars carry this pair, while the animals pull it down — exactly the kind of split the one-liner on the card points out, and why each line below the score links to its own game for the full explanation.

All three systems are traditions, not science, and the weights are our own choice. Read the result as a fun conversation, not a forecast for your relationship. The same two birthdays always give the same result, and each line under the card opens that pair in its own game so you can see the details.