Free Saju calculator: how a Korean four-pillars chart is worked out
A Saju calculator needs your birth date, your birth time if you know it, and where you were born (for the time zone). It turns them into four pillars using the 24 solar terms, not the calendar month, so the Saju year starts at Ipchun (around February 4), not January 1 or Lunar New Year. Enter your solar (Gregorian) birthday. If you only know your lunar birthday, convert it to the solar date first.
What the calculator uses
| Input | Why it matters |
|---|---|
| Birth date (solar / Gregorian) | Sets the year, month, and day pillars |
| Birth time | Sets the hour pillar (12 two-hour blocks). Optional: without it you get 3 pillars |
| Birth place time zone | Converts your local time correctly, including daylight saving time history |
Solar terms, not calendar months
Saju months begin on solar terms, the points where the sun crosses fixed positions in the sky. The first, Ipchun (Start of Spring), falls around February 4. Someone born on February 2 still belongs to the previous Saju year, even though the calendar year has changed.
Births within about half an hour of a solar term are "boundary births." A good calculator flags them, because a few minutes can change the month pillar.
Solar or lunar birthday?
Many Korean families celebrate a lunar birthday. A Saju calculator needs the solar date of the day you were born. If you only know the lunar date, convert it with a lunar-to-solar converter (check whether it was a leap month), then enter the solar date.
FAQ
Is the reading free?
Yes. On Saju Decode both the personal Saju card and the two-person relationship reading are free, with no sign-up. Birthdays are not stored.
What if I don't know my birth time?
Check "birth time unknown." You'll get three pillars. The Day Master and most of the element balance come from the date.
I was born between 11pm and 1am. Which day am I?
Schools disagree on whether the day changes at 11pm or at midnight. If your reading feels off, try the time on both sides of midnight and see which fits.
Do I need the city or just the time zone?
For Saju, the time zone at your birth place is what matters, including whether daylight saving time was in effect.
Free, no sign-up, birthdays never stored.
Calculate my Saju ✨