BaZi calculator
Free, no sign-up, and it shows its working. Enter when and where you were born. You get your four pillars and every correction step, so you can check them against any other source. It doubles as a Day Master calculator, naming the character the rest of your chart is read against.
What the result shows
Casting a birth returns the four pillars, with the day pillar marked: its top character, the day stem, is your Day Master. Under them is a reading of the Day Master and its strength. It names the month and season you were born in. It scores that strength in three parts: season, ground and visible help. The correction chain shows every step from your clock time to your hour branch. Add a gender and the result also lists the ten luck pillars, with the ages and years each one covers when the birth hour is known. Anything that depends on a birth time you did not give is left out, and the result says why. It also offers the reports written from that same chart — the full reading is the $39 natal report.
WORKED EXAMPLE —
NOT YOUR CHART — CAST YOURS ABOVEHOW THIS HOUR WAS DERIVED
MOST CALCULATORS STOP AT STEP 3
Where another site may differ
- A calculator that reads the hour straight off the clock, with no zone or longitude correction at all, gives 甲申; with the solar correction it is 癸未.
WHAT THIS CALCULATOR DOES THAT MOST DON’T
Each of these is demonstrated by a permanent test case in the verification corpus — follow the link on any point to see the worked case.
Historical time zones, not current ones
Singapore ran UTC+7:30 until 1982. Hong Kong observed summer time until 1979. Mainland China ran nationwide daylight saving from 1986 to 1991 — a cohort most calculators silently miscast, because they apply today’s offset to a 1980s birth.
SEE THE HISTORICAL TIME-ZONE CASE →The equation of time, not just longitude
Longitude alone gives Local Mean Time — a fictional, even-paced sun. The real sun runs up to ~16 minutes ahead or ~14 minutes behind it. Near a two-hour boundary, that difference decides the hour branch. Most calculators apply no equation of time at all.
SEE THE EQUATION-OF-TIME CASE →True solar time is not fed into the year pillar
A solar term is one worldwide astronomical instant. Some chains correct the clock to true solar time first, then compare that reading against the term table. Near Li Chun, that gets the YEAR pillar wrong. The New York case in the corpus shows a whole-year error.
SEE THE LI CHUN YEAR-PILLAR CASE →Daylight-saving edge times are flagged, not guessed
A birth time inside the spring-forward gap never occurred; inside the fall-back overlap it occurred twice. Both are detected here and warned about, rather than silently resolved to whichever instant the library prefers.
SEE THE DST EDGE CASE →Conventions this calculator applies
One published set of conventions rather than a menu of switches. It includes what the engine does not handle. So a chart cast here can be audited against any other source, and a difference can be named rather than argued. Each convention is stated in full, with the alternatives, on the methodology page; the cases above demonstrate the time-zone and equation-of-time ones.
- The year changes at Li Chun (立春), not at Chinese New Year
- Solar terms are compared against the birth instant, not its true solar time
- The hour pillar uses true apparent solar time, including the equation of time
- A birth between 23:00 and 23:59 keeps the current day pillar
- An unknown birth time produces three pillars, never a guessed fourth
- What this engine does not claim to handle
- Luck pillars (大運): direction, base, and onset age all come from the absolute-instant chart
- The engine is checked on every build against 34 published test cases — the verification corpus.
If your chart differs from another site
Usually one of four causes. The other site may read the hour off clock time instead of true solar time. It may use the opposing late-zi day boundary. It may set the day boundary at civil midnight instead of true solar time. Or it may compare a solar-corrected reading against the solar-term table, which shifts the year pillar near Li Chun. The list is not exhaustive. The conventions state which side this engine takes; the verification corpus shows several as worked cases.
Related
What the four pillars are · Finding your Day Master · The hour stem table · Luck pillars: the starting age · The 2027 forecast · Chinese zodiac 2027