Compatibility — What BaZi Actually Measures Between Two People

What it IS — a structural-fit reading

Two BaZi charts overlap on multiple dimensions. The compatibility engine surfaces the overlaps and labels them. It looks at how the two day masters interact on the elemental cycle. It checks every branch in chart A against every branch in chart B for clashes, combinations, and harms. It compares the elemental balance of one chart against the elements the other chart needs. And it asks how each day master would classify the other through the ten-god lens — the relational vocabulary BaZi uses to describe felt roles.

That’s the whole analysis. It’s structural and observational. It uses words like “structurally complementary,” “friction point,” and “supportive bond.” It does not use words like “destined,” “fated,” or “meant to be,” because none of those are measurable patterns in the chart.

The five things the engine checks

The compatibility report is built from five components, weighted as follows. The total composite score is capped at 0–100.

Each component is described in detail below. The most weighted signal in the model is the day-palace check — the contact between the two day branches — followed closely by the day-master elemental relation. Together they account for up to 60 of the 100 points. Everything else fine-tunes around them.

1. Day Master relation

The day stem is your anchor identity in BaZi. The first thing the engine checks is how the two day stems sit on the five-element cycle. Five outcomes are possible:

• Same element. Both day masters share an element (say, both Wood). Natural understanding, but also competition for the same resources and roles. Scored 22–24 depending on whether the two stems share polarity.
• Productive cycle (one produces the other).A’s element generates B’s, or vice versa — Wood feeds Fire, Fire feeds Earth, Earth feeds Metal, Metal feeds Water, Water feeds Wood. The strongest day-master signal in the model. Scored 28–30.
• Controlling cycle (one controls the other).A’s element overrides B’s, or vice versa — Wood controls Earth, Earth controls Water, Water controls Fire, Fire controls Metal, Metal controls Wood. The friction case. Scored 12. Productive only if the dominant side wields the pressure constructively.
• Neutral. The two elements neither produce nor control each other. Scored 20. The character of the pairing comes from the rest of the chart pair instead.

Important: a controlling-cycle pair is not a doomed pair. It just means the structural relation between the two day masters carries a directional pressure that has to be consciously managed rather than ignored. Plenty of working partnerships are built on a controlling cycle — the controlled side gets shape and structure, the controlling side gets something to direct. The frictionless version is the productive cycle. Both can work.

2. Day Palace signal

The day branch is read in BaZi tradition as the “spouse palace” — the position in the chart most associated with the closest emotional partnership. The engine treats the contact between the two day branches as the single most weighted cross-chart signal. Up to 30 points come from this one slot.

Five outcomes:

• Combination. The two day branches form a six-combination (say, Tiger + Pig forming Wood). The strongest cross-chart positive signal. Spouse palaces are structurally bonded. Worth 30.
• Same branch. Both day branches are identical (both Tiger, both Rabbit, etc.). Natural resonance, similar emotional reflexes. Worth 25.
• Same element. Different branches but the same element (say, Tiger and Rabbit, both Wood). Soft harmony — similar instincts even without a formal combination. Worth 22.
• Neutral. Neither bonded nor in conflict. Worth 18. The spouse palace is structurally quiet — read the rest of the chart for what the relationship will feel like.
• Harm. The two day branches form a six-harm. Quiet, low-grade friction at the closest emotional layer. Worth 10.
• Clash. The two day branches sit in direct clash (say, Rat and Horse). Spouse palaces collide, recurring friction at the closest emotional layer. Worth 5. This is the single most-watched friction signal in the report.

A day-palace clash is not a verdict. It is a pattern to be aware of and consciously offset with structure and communication. Read it as the model’s way of saying “there’s a consistent friction line at this contact — work around it on purpose rather than getting blindsided by it.”

3. Cross-chart branch interactions

Each chart has four pillars and four branches: year, month, day, and hour. The engine compares every branch in chart A against every branch in chart B — sixteen cross checks total — looking for three things: clashes (six pairs of opposite branches), combinations (six pairs of bonding branches), and harms (six pairs in low-grade friction). Every match is recorded with which positions are involved on each side.

These cross-chart matches are scored separately from the day-palace check. Each combination contributes +2to the cross-chart slot, each clash contributes −3, and each harm contributes −1. The total contribution is clamped to a maximum of ±15, so a chart pair with twelve overlapping combinations and twelve overlapping clashes won’t swing the headline number wildly. The clamping is deliberate: this slot is meant to fine-tune the score, not dominate it.

What matters more than the score is which pillars are in contact. A clash between A’s month pillar and B’s day pillar carries a different flavor than a clash between A’s hour and B’s year. The engine records the position pair with every interaction so the rendered report can show you the actual contact points, not just a count.

4. Elemental complementarity

Every BaZi chart has an elemental balance — a count of how much Wood, Fire, Earth, Metal, and Water the chart carries. Most charts are uneven, with one or two elements in surplus and one or two elements in deficit. The complementarity check asks: does one chart bring elements the other chart structurally lacks?

The engine looks at each of the five elements in turn. If chart A has at least 2.5 units of an element and chart B has less than 1.5 units of the same element, A is recorded as “providing” that element to B. Same check the other direction. The two surplus-supplies-deficit lists are then scored, with extra weight when the supplied element happens to be on the receiving chart’s favorable-element list (its 用神 — what the chart actually needs to balance its day master).

This is one of the most actionable signals in the model. What the other chart provides isn’t a metaphor — it’s actual elemental presence the strength calculation reads as support. A chart that’s dry on Water meeting a partner whose chart is full of Water reads as structurally supplied. The max contribution to the headline score is 25.

5. Ten God dynamic

The Ten Gods are BaZi’s relational vocabulary. From any day master’s perspective, every other stem in the chart gets labeled as one of ten roles — Friend, Rob Wealth, Eating God, Hurting Officer, Direct Wealth, Indirect Wealth, Direct Officer, Seven Killings, Direct Resource, Indirect Resource. These labels are not personality traits. They’re structural relationships between elements, viewed through the day master’s frame.

For compatibility, the engine asks: if A’s day master looks at B’s day master through the ten-god lens, what role does B play? And the same question the other direction. The result is a pair of labels — for example, “A reads B as Direct Wealth, B reads A as Direct Officer.”

Wealth and Officer cross-readings score highest (these are the classic “spouse signal” categories in BaZi tradition). Friend and Rob Wealth score lowest (they suggest peer competition rather than complementarity). Resource and Output sit in the middle. Total contribution caps at 15 points.

Treat the ten-god dynamic as a felt-role descriptor: it’s the model’s shorthand for what each person tends to represent for the other, structurally. It’s not a permanent identity. It’s how one day master classifies another at the level of the chart relation.

A note on symbolic stars: the engine computes symbolic stars (神煞 — Heavenly Noble, Peach Blossom, Travelling Horse, etc.) for each individual chart, but does not currently score cross-chart symbolic-star interactions in the compatibility report. Each individual reading still surfaces them, and they are visible in the side-by-side pillars view.

What each interaction kind means in plain English

Five interaction families show up across the natal charts and the compatibility report. Here’s what they actually mean when you see them on the page.

For a deeper walkthrough of these five families on their own, see Clashes & Combinations. The compatibility report uses the same vocabulary — it just applies it across two charts instead of within one.

How to read the result honestly

The compatibility tool returns a number between 0 and 100. The instinct, after seeing it, is to read that number as a verdict. Resist the instinct.

A high score is structural compatibility, not love. It means the engine finds many supportive structural overlaps and few friction points between the two charts. It does not mean the relationship will be effortless, that the two people will agree on values, or that attraction will hold over time. A high score on a pair of people who don’t actually like each other is meaningless.

A low score is structural friction, not doom. It means the engine finds more contact points carrying clashes, harms, or controlling-cycle dynamics than supportive ones. Real relationships built on a low structural score exist everywhere. The friction shows up as recurring patterns the two people consciously work around — not as a sentence.

The headline number is the worst part of the report. The valuable part is the breakdown: which pillars are in contact, which elements one chart provides the other, what role each day master plays for the other through the ten-god lens, and where the spouse-palace contact lands. Read those. Skim the score.

What the compatibility analysis CAN’T tell you

• Whether you should marry this person.
• Whether they are faithful, trustworthy, or kind — those are character measurements, not compatibility measurements, and they belong to each individual chart, not to the pair.
• Whether you will have children together.
• Whether your love will last. No test on earth measures this, including this one.
• Whether the other person is attracted to you, or you to them.
• Whether the relationship is the right one for the life you want.

These are not gaps in the model the site happens to use. They’re measurements no chart-based system can make, anywhere, ever. Any tool that claims otherwise is either guessing or selling something.

What it CAN tell you, with calibration

• Where structural friction is likely to show up — which pillar-to-pillar contacts carry a clash or a harm.
• Where you and this person likely complement each other on element balance — which surplus elements one chart brings to the other's gaps.
• What ten-god label each day master assigns the other — structural shorthand for the felt role the other person tends to play.
• Whether your day masters tend to read in the same key (productive cycle) or in different keys (controlling cycle, or no cycle at all).
• Whether the spouse-palace contact — the closest cross-chart layer — bonds, opposes, or sits quiet.

Calibration matters. “Can tell you” means the model produces these signals reliably from the chart data — not that they’re universally correct. They’re structural observations. Treat them the way you’d treat a personality test result: useful for noticing patterns, useless as a verdict on a person.

A worked example

Take a Yang Wood day master (甲, Jiǎ) paired with a Yin Fire day master (丁, Dīng). Wood produces Fire on the five-element cycle. The engine reads this as a generative pairing in the Wood-to-Fire direction — Wood feeds Fire, the day-master relation scores 30 out of 30, and the polarity flag is “strongly supportive.”

Practitioners read this as cooperative. In practice, that doesn’t mean the relationship will be easy. It means the two people’s day masters tend to read in compatible keys, the way two musicians tuned to the same scale can play together without thinking about the tuning. The Wood side will, structurally, feel like it has something to give. The Fire side will, structurally, feel like it’s being fueled. Whether that feels nourishing or draining over time depends on whether both sides notice the dynamic and agree to it. The friction in any real relationship comes from values, communication, life stage, and circumstance — none of which the chart reads.

The same Yang Wood day master paired with a Yin Metal day master (辛, Xīn) reads differently. Metal controls Wood on the five-element cycle. The engine scores this 12 out of 30 and flags it as a challenging-polarity pairing — the controlled side (Wood) carries a structural pressure from the controlling side (Metal). That doesn’t mean the pairing fails. It means the dynamic has a directional edge that needs to be consciously softened, especially from the Metal side, for the Wood side to thrive. Many working partnerships are built exactly here. The model is just naming the shape.

And then the rest of the report runs on top of those day-master scores: the spouse-palace contact between the two day branches could add up to 30 more points, the cross-chart branch interactions could swing the total ±15, the elemental complementarity could add up to 25, and the ten-god dynamic could add up to 15. The day-master relation is the opening line of the analysis. Everything else is the rest of the conversation.

Limits

Classical BaZi compatibility doctrine has many schools. Different lineages weight different things. Some practitioners build the compatibility analysis primarily on the year-pillar contact (the Chinese-zodiac-animal layer most popular media uses). Some weight the day-master relation above all else. Some emphasize useful-god (用神) supply between the two charts. Some focus on the natal structures (格局) of each chart and how they slot together. There is no single agreed methodology.

The compatibility tool on this site uses one defensible methodology: day-master elemental relation, spouse-palace contact, cross-chart branch interactions, elemental supply between the two charts, and the ten-god classification each day master assigns the other. Other practitioners may weight these differently or include things this site leaves out (like cross-chart symbolic-star contacts, cross-chart structure interactions, or palace-by-palace ten-god overlaps). When two BaZi compatibility tools give different results for the same pair, that’s usually why — they’re computing different things.

The site’s compatibility report is built to be honest about what it’s doing. The headline number is a composite, the components are listed and weighted explicitly, every interaction is shown with its position pair, and the disclaimer sits at the top of the rendered report rather than buried at the bottom. It is one structured, defensible reading — not the only one possible. Use it for what structural analysis is good for: spotting patterns, naming friction points, and surfacing what each chart brings to the other. Use other tools — including the messy, unmeasured ones like attention and conversation — for the rest.

How it connects

• The Compatibility Tool — run two charts through the engine described on this page and see the report.
• Clashes & Combinations — the five interaction families this report uses, explained on their own terms.
• The Ten Gods — the relational vocabulary the ten-god dynamic component is built on.
• Limits of BaZi — what BaZi as a whole can and can’t measure. The compatibility tool sits inside those limits.