Free tool
Saju calculator
Korean Four Pillars of Destiny, in English. Your year, month, day and hour pillars, your day master, your five element balance, and the ten-year luck cycles you move through — with the solar term boundaries computed astronomically rather than looked up.
How Saju differs from a zodiac sign
Saju (사주, 四柱) means "four pillars." Each pillar pairs one of ten heavenly stems with one of twelve earthly branches, giving four stem and branch couples for the year, month, day and hour of your birth. Eight characters in total — which is why the same system is called Ba Zi, "eight characters," in Chinese.
The pillar that matters most is the day stem, your day master. It stands for you, and every other character in the chart is read as a relationship to it: what supports you, what drains you, what you control, what controls you.
Your Saju year does not start on January 1
It starts at ipchun (입춘), the solar term when the Sun reaches 315 degrees of ecliptic longitude — usually February 4. Someone born on January 20 belongs to the previous Saju year, and a great many online calculators get this wrong, handing people the wrong animal and the wrong year pillar entirely. We solve for ipchun from the Sun's actual position.
Months turn at solar terms too
The month pillar does not follow calendar months or lunar months. It turns at the twelve major solar terms, each 30 degrees of solar longitude apart. Your month pillar is set by where the Sun actually was.
True solar time
Hour pillars are solar, but clocks are political. Korea keeps time on the 135°E meridian while Seoul sits near 127°E, so Seoul clocks run roughly 32 minutes ahead of the local sky. Near an hour boundary that gap changes your hour pillar, so we correct for the meridian you were born on.
Read it against your natal chart
Saju and Western astrology were built from the same sky by people who never compared notes. Running both from one birth moment is where things get interesting — the full reading is built on exactly that comparison.