Korean 궁합 (gunghap), Chinese 合婚, and Japanese 相性 all ask the same question: when you put two people's charts side by side, what happens? The popular version turns this into a single percentage — "you're 78% compatible" — but a real reading is not one number. It is several different relationships between the two charts, and they can disagree with each other. This guide explains the three that matter most, and why a high score and an easy relationship are not the same thing.
Every chart is read through its Day Master — the heavenly stem of the day pillar, which stands for the person themselves. In compatibility, the first thing you compare is one person's Day Master against the other's. Are the two stems the same element, elements that generate each other, elements that control each other, or unrelated?
A generating pair (one person's element feeds the other's — wood feeding fire, water growing wood) tends to read as nourishing: one naturally supports the other's growth. A controlling pair (one element disciplines the other — metal cutting wood, water quenching fire) reads as friction, but friction is not automatically bad. Control is how excess gets shaped; a person whose chart runs hot can be steadied by a partner whose element cools them. Same-element pairs understand each other instantly and can also amplify each other's blind spots, since neither supplies what the other lacks. None of these is a verdict — they are starting tendencies. If you don't yet know what a Day Master is, start with the 10 Day Master archetypes.
Below the Day Master sits the Day Branch — the earthly branch of the day pillar, which classical practice ties to the marriage and partnership "palace." Comparing the two Day Branches surfaces two of the most-cited relationships in 궁합: harmony (合, hap) and clash (충, chung).
A harmony between Day Branches reads as ease — a sense that the two of you slot together without forcing it, that being in the same room is restful. A clash reads as charge — magnetic, intense, the kind of pairing that feels alive but rarely feels calm. This is the part people misread most: a clash is not a failure signal. Many of the most enduring pairings carry a Day Branch clash, because the tension is what keeps the relationship awake. The honest reading is not "harmony good, clash bad" — it is knowing which one you have, so you stop expecting a clash to feel like a harmony.
The third relationship looks past the day pillar at the whole elemental picture. Each chart has a five-element distribution — some elements strong, some weak, sometimes one missing entirely. (If that idea is new, the five elements balance guide covers it.) In compatibility, you ask: does each person carry the element the other is short of?
When one chart is heavy in fire and thin on water, and the partner's chart runs deep in water, each one quietly supplies the other's missing medicine — the classical idea of the useful god (用神), now operating across two people instead of one. This is the most underrated layer of 궁합, because it does not show up as instant chemistry. It shows up over years, as the slow sense that you are steadier, more complete, more yourself when this person is around. Two charts can have an unremarkable Day Master pairing and still complement each other beautifully at the element level.
The three layers do not have to agree. You can have a harmonious Day Branch and no element complement — comfortable, but neither person grows. You can have a Day Branch clash and a strong element complement — turbulent on the surface, deeply stabilizing underneath. The single-number compatibility scores you see everywhere collapse all of this into one figure and throw away exactly the information that would have been useful.
A real reading keeps the layers separate and tells you the shape of the relationship: where the ease is, where the friction is, and whether the friction is the productive kind that shapes both people or the draining kind that just wears them down. "78% compatible" tells you nothing you can act on. "You harmonize easily but neither of you supplies the other's missing element, so you'll need to build growth in on purpose" — that you can use.
It is worth being plain about the limits. A chart comparison describes tendencies in how two temperaments meet — it does not predict whether a relationship lasts, and it is not a reason to start or end one. People with "difficult" comparisons build wonderful lives together; people with "ideal" ones grow apart. What the reading does well is name the dynamic you are already living, so that the friction stops feeling like a personal failure and starts looking like a known pattern with known handles. Treat it as a mirror, not a verdict.
To compare two charts properly you need both people's full birth dates and, ideally, birth times — the Day Branch and the element balance both depend on the day and hour pillars, and the month pillar shifts on the 24 solar terms (節氣), not the calendar month. With approximate times you can still read the Day Master and element layers; the Day Branch harmony/clash layer needs the day pillar, which is date-driven and reliable even without an exact hour.
You can run a free two-person comparison — Day Master pairing, Day Branch relationship, and element complement, with the method shown openly — here: hoonsikim.github.io/saju/compat.html. Two birth dates, one reading, no signup and no email.