Most "compatibility calculators" match two zodiac animals and call it a day — which throws away seven eighths of each chart. A real one compares two complete charts and weighs the factor popular tools never mention: whether each person's chart carries the element the other is starving for. Here's what's actually free, what the comparison checks, and how to read it — including how to do it yourself.
Straight answer, because this corner of the internet is full of "free" that isn't: computing the charts is free; the comparison is the work.
If a tool claims a complete compatibility reading for free, check whether it's actually reading each chart's useful element or just matching your birth-year animals. The second one is free because it's worth nothing.
Not your birth-year animals. A proper BaZi compatibility calculator builds both Four Pillars charts in full and compares them on four layers, in order of weight:
| Layer | What it compares | Weight |
|---|---|---|
| Elemental supply | Does each chart carry the other's useful element (用神)? | Heaviest |
| Day Masters | How the two Day Stems interact — feed, control, or combine | High |
| Spouse Palaces | The two Day Branches: harmony, clash, harm, or punishment | High |
| Spouse stars | Is the partner star present, strong, and undamaged? | Medium |
The full mechanics of each layer are in the BaZi compatibility guide. What matters for reading a calculator's output is knowing which number is load-bearing — and it's the first one.
Every chart has a useful element — the one it most needs to come into balance. Compatibility largely reduces to a single question: does their chart carry your useful element in quantity, and does yours carry theirs?
This is why a good calculator has to read each chart alone first. A tool that jumps straight to "your animals are compatible" has skipped the entire foundation. If a calculator can't tell you each person's useful element, it can't actually assess supply — and supply is the whole ballgame.
A single percentage is a convenience, not a verdict. Read the breakdown, not the headline number:
Ideally yes, but you keep most of the compatibility signal without them. The Hour Pillar adds the reading on children and later life; the Day Pillar — Day Master and Spouse Palace — carries the core, and you keep that from the date alone. A partial read on real data beats a complete read on an invented birth time. If either time is unknown, see BaZi without birth time.
Ming computes your Four Pillars deterministically — the exact stems and branches for your birth moment — then explains them in plain English. No signup, no guessed pillars.
Open the BaZi Calculator →Partly — and be suspicious of anyone claiming otherwise. Computing each chart is free and always should be: run Ming's calculator once per person for both full charts, no signup. The four-layer comparison is the actual work — you can do it yourself with the method on this page, or Ming's Compatibility Report ($6.99, or included in $29.99/year) does it for you. Anything advertising a complete free compatibility reading is usually just matching birth-year animals.
It builds both people's Four Pillars, then compares them on four layers: whether each chart supplies the other's useful element (the heaviest factor), how the two Day Masters interact, what happens between the two Spouse Palaces (harmony, clash, harm, punishment), and whether each spouse star is present and healthy.
No — that's the popular version and it's nearly useless. Animal matching compares one character (your year branch) out of eight and ignores the rest. Real BaZi compatibility compares all sixteen characters across two charts and weights the Day Pillar, where the marriage actually sits.
Whether each chart carries the element the other most needs — the useful element (用神). A partner who brings your favorable element feels steadying; one who piles on the element you already have in excess feels exhausting, even when the animal-match score looks high. Read the breakdown, not just the percentage.
No. A Spouse-Palace clash means friction, movement, and change, not doom — and it can even help when it releases an element your chart needed. Many long marriages contain a clash. What matters far more is whether each chart supplies the other's useful element.