Nine Star Ki Calculator
Your year, month and tendency stars, timed to the exact moment the solar year and month turned.
Use the local clock time and the UTC offset of the place you were born. The time only matters if you were born within a day of a solar-term change; the result will tell you if you were.
Nine Star Ki (九星気学, Kyūsei Kigaku) is a Japanese system of astrology built on the Lo Shu, the three-by-three magic square in which every row, column and diagonal adds up to fifteen. Each of its nine numbers is a "star" with an element, a trigram of the I Ching and a compass direction. As the years and months pass, the stars move through the square in a fixed order, and the star at the center when you were born colors your nature.
Most free tools stop at the year star. This one gives you all three numbers that Nine Star Ki readings are usually written with, such as 1.3.3 or 6.4.7:
- Year star (principal, 本命星 honmei-sei): your adult character and the way you meet life.
- Month star (character, 月命星 getsumei-sei): your emotional make-up, how you were as a child and how you react under pressure.
- Tendency star (energetic): the impression you make and the way you tend to act, read from the relationship between the first two.
The year starts in February
Nine Star Ki follows the solar calendar, not 1 January and not Lunar New Year. The Ki year begins at Risshun (立春, Li Chun in Chinese), the moment the Sun reaches 315° of ecliptic longitude, which falls on 3, 4 or 5 February. Each month begins at one of the twelve solar terms, every further 30° of the Sun's path, around the 4th to 8th of each month. Anyone born in January or in the first days of February therefore belongs to the previous Ki year.
This calculator does not use a fixed "4 February" rule. It computes the Sun's apparent position for your birth moment with a full planetary model and finds the exact instant of each boundary, so a birth a few hours either side of a solar term lands on the right side.
How the numbers are worked out
Year star. Take the Ki year, find its remainder when divided by 9, and subtract it from 11 (reduce to 1–9 if needed). 2024 gives 3, 2025 gives 2, 2026 gives 1 and 2027 gives 9: the year star counts down by one each year.
Month star. The month star is the star at the center of the square for your solar birth month. In Rat, Rabbit, Horse and Rooster years the first month (the Tiger month, from Risshun) is ruled by 8; in Ox, Dragon, Goat and Dog years by 5; in Tiger, Snake, Monkey and Pig years by 2. Each following month counts down by one, so in 2026 the months run 8, 7, 6, 5, 4, 3, 2, 1, 9, 8, 7, 6.
Tendency star. Place your month star in the center of the Lo Shu and let the other numbers follow in their usual order. Find the palace your year star now occupies. The number that normally lives in that palace, in the standard square with 5 at the center, is your tendency star. In arithmetic terms it is 5 plus the year star minus the month star, reduced to 1–9, which is why anyone whose year and month stars match has 5 as their third number.
- 1 White Water · Kan (Water) · North
- 2 Black Earth · Kun (Earth) · Southwest
- 3 Jade Wood · Zhen (Thunder) · East
- 4 Green Wood · Xun (Wind) · Southeast
- 5 Yellow Earth · no trigram · Center
- 6 White Metal · Qian (Heaven) · Northwest
- 7 Red Metal · Dui (Lake) · West
- 8 White Earth · Gen (Mountain) · Northeast
- 9 Purple Fire · Li (Fire) · South
Frequently asked
What is Nine Star Ki?
Nine Star Ki (Kyūsei Kigaku) is a Japanese form of astrology that grew out of Chinese Lo Shu numerology and Flying Star feng shui and took its modern shape in Japan in the early twentieth century. It assigns each solar year and month one of nine stars, each linked to an element, a trigram and a direction, and reads a person through the stars ruling their birth year and birth month.
How is my Nine Star Ki year star calculated?
First find your Ki year: if you were born before Risshun (the moment the Sun reaches 315°, on 3, 4 or 5 February), use the previous calendar year. Then divide that year by 9, take the remainder and subtract it from 11, reducing the result to 1–9. For example 2024 gives 3, 2025 gives 2 and 2026 gives 1.
How is the month star found?
Months turn at the solar terms, not on the first of the month. The first Ki month starts at Risshun and is ruled by 8 in Rat, Rabbit, Horse and Rooster years, by 5 in Ox, Dragon, Goat and Dog years, and by 2 in Tiger, Snake, Monkey and Pig years. Each later month is one lower, and after 1 comes 9. The star ruling your solar birth month is your month star.
How is the third (tendency or energetic) number calculated?
Put your month star in the center of the Lo Shu square and fly the other numbers forward in the usual order. See which palace your year star lands in; the number that sits in that palace in the standard square (with 5 in the center) is your third number. As a formula: 5 + year star − month star, reduced to 1–9. Examples: born 15 July 1990 gives 1.3.3; born 25 December 1985 gives 6.4.7; born 4 February 2000 before 20:40 Beijing time gives 1.6.9, and after it 9.5.9. The third number is used mainly in Western Nine Star Ki teaching; many Japanese practitioners work with the year and month stars alone.
Why do my birth time and time zone matter?
The year and each month change at an exact astronomical moment, not at midnight. If you were born within about a day of one of these solar terms, the hour and the time zone of your birthplace decide which side of the line you fall on. The calculator tells you when that is the case and shows the numbers you would have on the other side.
Why is my year star not the one for my Chinese zodiac year?
The Chinese zodiac animal usually changes at Lunar New Year, which moves between late January and mid-February. Nine Star Ki, BaZi and feng shui all change the year at Risshun instead. A birth between the two dates can have a zodiac animal from one year and a Nine Star Ki year from another. Both conventions are legitimate; this calculator uses Risshun throughout.
Is this calculator free?
Yes. It is free, needs no sign-up and runs entirely in your browser; your birth details are not sent anywhere. The full Arcana Origin reading adds your Feng Shui Kua number, BaZi Four Pillars and many other traditions from the same birth moment.
See your stars in the whole chart
Nine Star Ki is one lens. Your full Arcana Origin reading sets it beside your BaZi pillars, your Kua number and the other traditions the engine computes from the same birth moment.
Cast your full reading →