House Overlays Synastry Calculator

This tool places each person's planets into the other person's houses and summarizes where the overlay emphasis lands. Birth time matters because house placement depends on angles.

House overlays can describe where a relationship is felt, but they do not prove compatibility, consent, emotional safety, marriage, durability, past-life ties, or whether a relationship should continue. Treat heavy overlays as topics to examine, not a verdict.

A house overlay shows which of your partner’s life areas each of your planets emphasizes. You take your natal planets, drop them onto your partner’s house wheel, then do the same in reverse. The planet person colors the house person’s life area; the house person usually feels that overlay most directly. Houses 1, 4, 5, 7, and 8 carry the highest relationship weight.

That’s the textbook definition. The thing the textbook leaves out is the asymmetry. The house person’s life is already there, with its rooms and weather and photos on the wall and old wiring behind the drywall. Your planet doesn’t build a new house. It walks into a room they were already living in and brings attention to that room.

The output above shows two columns. Your planets in their houses, then their planets in your houses. Most people stop reading at the first column. Don’t.

The first thing to scan for is clusters. If three or four of your planets land in their 7th house, you emphasize their partnership zone in a way no single contact does. Same for any house. Three slow planets in their 12th is a different relationship than three fast planets in their 5th.

Then read the planet person vs house person dynamic for each row. The planet person brings the planetary tone; their Mars walks into a room, their Venus brings a particular kind of attention. The house person receives, but more importantly, lives there. The room belongs to them. Their existing patterns in that area are the soil. Your planet is what gets planted.

People get this backward all the time, so it’s worth saying directly. The house person almost always feels the overlay more.This is counterintuitive because the planet person seems like the doer. But the house person is the one with skin in the game; it’s their 4th, their 8th, their 10th. The planet person feels the pull. The house person feels the weather change.

Not all of them, and not equally. There are five that usually feel most noticeable in relationship work and seven that color it.

The five that move it: 1, 4, 5, 7, 8

1st house overlays are about chemistry and presentation. When their Sun lands in your 1st, you feel like you become a brighter version of yourself around them. When their Saturn lands in your 1st, the opposite can happen, often a quieter or more constrained version. 1st-house overlays are visible. Other people may read the relationship off your face.

4th-house overlays are about what happens behind closed doors. Their Moon in your 4th can describe domestic ease or home-life familiarity; their Pluto in your 4th can describe pressure around roots, family, or private life. 4th house contacts are often felt in the emotional foundation of the relationship.

5th-house overlays are about play, romance, creative output, and children, in roughly that order of frequency. Their Venus in your 5th is the easiest contact to enjoy. Their Saturn in your 5th is the contact that makes you want to grow up.

7th-house overlaysget the most press. Here’s the thing about the 7th, though: it’s the house of partnership, which means it’s also the house of projection. When their planets land in your 7th, you tend to see them as a partner whether they actually are one. The 7th is a strong contact for partnership projection, not proof of marriage. Reading 7th-house overlays well requires you to ask which one’s actually happening.

8th-house overlaysare the underrated ones. The 8th is sex, shared resources, vulnerability, and what each of you brings to the relationship that the other has to swallow. 8th-house contacts are where actual relationships can live, after the 7th-house glow wears off. The first time you fight about money, that’s the 8th house. The first time you let someone see you scared, that’s the 8th house. If a relationship has 7th-house overlays without 8th-house overlays, the practical layer may need extra attention.

The seven that color it

The other houses set context but don’t set the relationship’s direction.

• 2nd-house overlays: values, money you each bring in, what you find pleasurable and worth keeping.
• 3rd-house overlays: how you talk to each other, day-to-day texts, sibling-like familiarity.
• 6th-house overlays: routines, maintenance, the ordinary stuff that shows whether you can actually live together.
• 9th-house overlays: shared worldview, travel, education, the relationship’s ideology.
• 10th-house overlays: how the relationship looks to the world, status, public role.
• 11th-house overlays: friend group, shared hopes, whether you become each other’s “person” in the social fabric.
• 12th-house overlays: the unconscious, hidden patterns, what gets carried in from past relationships, projection, or unspoken expectations. The 12th rewards therapy.

You may feel the first five before you feel the second seven. The second seven help explain whether the first five can be lived.

This is the field guide. The full meaning depends on which house, but the planet’s flavor stays consistent.

• Sun: identity emphasis. They may remind you who you are in that area.
• Moon: emotional resonance. They may make that area feel more familiar, tender, or reactive.
• Mercury: communication current. You talk about that life area, a lot.
• Venus: pleasure and harmony. They make that area feel beautiful or worth softening for.
• Mars: drive, friction, sexual current. They push you to act there, sometimes by fighting you about it.
• Jupiter: expansion. That area grows; can also get bloated.
• Saturn: weight and time. That area gets serious; you’ll either build something there or feel limited there. Saturn contacts last.
• Uranus: disruption. That area can become unpredictable. It may break stagnation, routine, or both.
• Neptune: dissolution and idealization. You see that area through a softer lens, for better or worse.
• Pluto: intensity and transformation themes. That area may feel hard to treat casually.

For the angles and nodes: Ascendant overlays mean your planet sits on their public-facing edge, affecting how they show up in the world. Midheaven overlays emphasize career and public role; strong contacts here often produce mentor or business-partner relationships. North Node overlays can feel like you are pushing them toward a growth direction already present in their chart.

Most synastry guides hand-wave here. They tell you to ignore Uranus, Neptune, and Pluto in overlays because they move slowly and you share them with everyone in your generation.

That advice is half right.

The half that’s right: if you and your partner are within a couple of years in age, your outer planets sit in the same signs. So a Pluto-in-Scorpio overlay between two 1985-borns isn’t telling you something specific about the two of you.

The half that’s wrong: outer planets still occupy specific housesin each chart, and those house placements are individual. Your Pluto might be in your partner’s 8th while their Pluto is in your 4th. That’s a real piece of information about how each of you transforms the other, even if the sign is shared.

The cleaner rule: read outer planet overlays for the house contact, not the sign. Weight them more when they hit an angle (Ascendant, IC, Descendant, MC) or a personal planet (Sun, Moon, Mercury, Venus, Mars) of the partner. Pluto on someone’s Sun is enormous regardless of generation. Pluto in their 6th house might just mean you reorganize their Tuesday afternoons.

You may run two calculators and get different houses. That’s not a bug. It’s a house system question.

Augurine defaults to Whole Sign houses, the system used by most Hellenistic astrologers and the one you’ll find in Vettius Valens, Dorotheus of Sidon, and modern practitioners working in that tradition. Whole Sign uses the Ascendant’s signas the 1st house and assigns each subsequent sign to the next house in order. A planet’s house placement is determined by its sign relative to the Ascendant. The result is clean, often surprising overlays.

If you switch to Placidus, the houses are calculated using the planet’s exact ecliptic longitude relative to time-based cusps. Planets near a cusp can fall on either side depending on minutes of birth time. A Mars at 28° Aries might be in the partner’s 7th in Whole Sign and the 8th in Placidus, simply because Placidus draws cusp boundaries differently.

If you want to see all eight major house systems side by side for a single chart, our house system comparison calculator will show you which systems agree and which disagree for your specific data. For overlays, my recommendation: start with Whole Sign, then check Placidus for any planet within five degrees of a sign boundary. If they tell different stories, you’re looking at a borderline case where both interpretations have something to say.

Overlays require accurate birth times for both people. If one of you doesn’t have a verified time, the houses are guesswork, and so is every overlay reading downstream.

Three options, in order of accuracy.

1. Get the time.Birth certificates often list it. Hospital records do. In some U.S. states the time appears on the long-form certificate but not the short-form, so order the long version. In countries where it isn’t recorded officially, ask the parent who was there.
2. Rectify. If there’s no record, our birth time rectification tool walks you through using major life events to back-calculate a probable birth time. It isn’t perfect, but it’s better than picking noon.
3. Read sign contacts only. If neither option works, you can still read the planetary signs against each other and skip the houses. The overlay calculator above will return houses regardless of birth-time accuracy, which means a noon-default time produces someanswer, just not necessarily the right one. Don’t over-invest in those houses.

A tight rule: if the Ascendant could plausibly be in either of two adjacent signs (which happens when birth time is uncertain by more than ninety minutes), don’t trust any house in the chart.

These three tools answer different questions. Overlays show you wherein each person’s life the contact lives. Synastry aspects show you how the planets between you talk to each other, harmoniously, with friction, or with the kind of intensity that makes you both flinch. Composite charts show you the third entity of the relationship itself, calculated from midpoints between your two charts. Davison charts do the same but use a real moment in real space, the time and location halfway between your two births.

If overlays are the “where,” aspects are the “how,” and composite is the “what we are together.” All three are real layers; none of them replaces the others. Most people start with overlays because they’re the most legible, then graduate to aspects, then go to composite when the relationship gets serious enough to think of as its own being.