u/Last_Paint

Saju is the Korean take on the four pillars system, also known as BaZi.

Same idea as a natal chart, different machinery. Instead of planets it reads the year, month, day and hour you were born as eight characters, and looks at how the five elements balance out across them.

I'm Korean and I've spent about a year building tools around it. The thing I kept hitting was that there's almost nothing in English for someone just starting.

So I wrote a beginner's book. It was going to be a paid ebook. It's online for free instead, no signup.

https://qiora.app/learn

14 chapters, from what the four pillars actually are to finding your day master and reading what it says about you. There's a reference section as well.

Happy to answer questions if anyone has them.

Five months ago, I posted here about a free Saju (BaZi) calculator I'd spent 6 months building. I expected maybe a dozen replies. I got 235 comments and a lot of DMs.

I read all of it. Here's what happened since.

The numbers:

Tens of thousands of charts, from over 100 countries. Almost all of it in English. More interest than I ever expected for something this niche.

The chart calculator is still free, still no signup. That part hasn't changed and won't.

What people actually asked for:

By far the most repeated request: "my city isn't in the list."

Birth location matters more than people assume. The hour pillar depends on true solar time, and true solar time shifts with longitude. A place 200km east of the city you picked can land you on a different hour pillar, and that's a quarter of the chart.

So for a while I just added cities by hand, one request at a time. That obviously didn't scale. Now there's a map. You drop a pin on where you were born, anywhere, down to a small island, and it uses the actual coordinates.

A few DMs asked about running two charts together. I figured that one would land, so compatibility is the first reading I built. Full natal readings are live too.

What I got wrong

The prompt feature. I built it as a side thing to pull traffic to the free calculator. I thought the calculator was the product and the prompt was a bonus. It was the opposite. Most people came for the chart and stayed for the prompt. That flipped my roadmap entirely.

What I learned about LLMs and structured data

The original reason I built this was to test whether an LLM could interpret a chart properly given accurate input. Five months of watching people use it: yes, clearly. The failure mode was never the model. It was the data going in.

Every "AI saju" tool I tried before was letting the model guess the chart, and a wrong chart roduces a confident wrong reading.

Free calculator, same as before: https://qiora.app/chart

Feedback is always welcome, especially from anyone who knows BaZi well.

And honestly, a lot of what's here came from comments on that post. If you're curious about the paid readings, DM me your account email and I'll open one for you, free. I owe this place. Thanks for the last five months.

I wrote A free beginner's guide to Korean saju

5 months ago I posted my free K-Saju / BaZi calculator here. Over 235 comments later, here's what I built and what I got wrong.