Free tool

BaZi calculator

Enter a birth date, a time and a city. You get the four pillars as characters, the Day Master, and how the five elements are distributed — calculated on this device, with nothing sent anywhere.

Updated October 2026

Date of birth

Gregorian. The conversion to the Chinese calendar is done for you.

Time of birth I don’t know my birth time
Worked from 12:00 local time and labelled as assumed. The element distribution is flagged approximate.

The clock reading as it was recorded where you were born, daylight saving included. The correction to solar time is handled here — you do not need to work it out.

Calculate the four pillars

What a BaZi calculator actually computes

“BaZi” (八字) means eight characters. A chart is the year, month, day and hour of birth, each written as a heavenly stem stacked on an earthly branch — four pairs, eight characters, four pillars.

Going from a birth certificate to those eight characters takes five conversions. Each one is a place a calculator can quietly go wrong, and none of them are visible in the output.

1. Undo the daylight saving that applied that day

A clock reading is not a physical quantity. It is whatever offset the relevant government had legislated for that date, and those offsets have changed repeatedly. Some countries have started and stopped daylight saving within living memory; some changed their standard offset outright.

A calculator that applies today’s offset to a birth in 1990 is wrong by an hour for half the year, and an hour is often enough to move the hour pillar to the next one.

2. Convert clock time to true solar time

The traditional reckoning runs on local solar time: when the sun was actually at its highest where you were standing. That differs from standard time for two reasons. Longitude, because a timezone is up to fifteen degrees wide and four minutes of time per degree. And the equation of time, because the sun runs fast or slow against a mean clock by up to about sixteen minutes across the year.

Both corrections need a birthplace. Without one, a calculator is implicitly assuming you were born on the central meridian of your timezone, which most people were not.

3. Find the year pillar — which does not change on 1 January

The year pillar turns over at Lichun, the solar term that begins spring, which falls around 4 February. Anyone born in the first weeks of January or the first days of February still belongs to the previous year’s pillar, whatever the Gregorian year says.

4. Find the month pillar — which does not follow the moon

The twelve months of a chart are bounded by the twelve jie solar terms, not by new moons. The month pillar changes when the sun crosses a given solar longitude, which happens a day or so earlier each year, so a month pillar can never be read off a calendar date alone.

5. Find the day pillar — a sixty-day cycle with no astronomy in it

Days run through an unbroken cycle of sixty, counted continuously for centuries. There is no observation involved and nothing to correct for: given a date, the day pillar is arithmetic. It is also the pillar that supplies the Day Master, the element traditionally read as the person.

6. Find the hour pillar

Twelve double-hours, each two hours of solar time. The branch comes from the clock; the stem is then derived from the day stem by a fixed rule, so the hour pillar cannot be computed before the day pillar is settled.

Two places the shortcut goes wrong

Both examples below are real output from the calculator above, not illustrations.

Why two calculators give two different charts

Because they disagree about the steps above, not about the rules. The four pillars are produced by a well-defined procedure; the ambiguity lives entirely in the inputs — which offset was in force, which meridian was used, where the year boundary was placed.

So the useful question is not which calculator is right, which you cannot check from the outside. It is which one shows enough for you to check it. That is a separate page: six checks you can run on any BaZi calculator. For where the chart itself can be tested and where the reading stops being testable, see how accurate BaZi is.

The four pillars, and what each is read as

• Year — the cohort you were born into, and the basis of the zodiac animal. The loudest pillar in popular writing and the least personal.
• Month — the season of your birth, and traditionally the strongest single influence on a chart. A supportive month counts for more than a supportive year.
• Day — the pillar read as you. Its stem is the Day Master, the element most people mean when they ask what their element is.
• Hour — the later life and the private register. Also the pillar most often wrong, because it is the one that depends on the time of day.

What this calculator does not do

• It does not interpret for you. It gives you the chart and the distribution. Reading meaning into them is a separate act, and one where practitioners disagree.
• It does not predict. The Five Elements describe balance and tendency. They are not a forecast, and they are not medical, psychological or financial advice.
• It does not hide a guess. If you tick the unknown-time box, the hour pillar is worked from 12:00 local time and labelled as assumed, and the distribution is flagged approximate. The number is shown because a chart without an hour pillar cannot be compared against another calculator — but it is not passed off as known.
• It does not go before 1900. Timezone and daylight-saving records get thin, and the hour pillar stops being trustworthy.

Questions people ask about this calculator

Is it free?

Yes. The four pillars and the element distribution are free, with no account, no email and no card. There is a paid written report, but the calculation is never gated behind it.

Do you store my birth details?

No. The calculation runs in your browser and the date, time and city are never sent to a server. They are kept in this browser’s local storage so the next page can read them, and reloading the form clears it.

Why is my element different from my Chinese zodiac sign?

They are two different things, and they are supposed to disagree. The zodiac animal comes from the year pillar alone. The element read as the person comes from the day pillar, and day pillars advance through a sixty-day cycle that does not line up with the year. Most people’s day element is not their year element. More on that here.

Do I need my exact birth time?

Not for the first three pillars. Year, month and day do not depend on the hour, and the Day Master comes from the day. You lose one pillar of four — which is why the unknown-time box exists rather than a compulsory field. What happens when the time is missing.

Does it work before 1900?

Not reliably. Timezone and daylight-saving records get thin before the twentieth century, so the hour pillar in particular becomes a guess. 1900 onwards is the supported range.