House overlays in synastry: where their planets land in your rooms

Run a synastry chart and the grid gives you aspects: this angle to that angle, a number of degrees, an orb. House overlays are a separate layer entirely, and it is worth being precise about what "separate" means here. An aspect tells you two planets are in a geometric relationship to each other, full stop, no third party required. An overlay tells you where one person's planet sits inside the other person's house structure - a structure that only exists once you know where and when that second person was born, because houses are built from the horizon and the meridian at a specific place and moment. Two different questions, two different kinds of data, and conflating them is one of the more common ways a synastry reading goes sideways.

What the overlay actually measures

When B's Venus lands in A's fourth house, that is not an aspect. B's Venus may or may not be making a contact to anything of A's - it might sit there in isolation, untouched by any of A's planets, and still be doing something, because it is occupying a room in A's chart. The house it falls in describes the area of life the other person's planet activates by its mere presence, independent of what it does geometrically. A's fourth house is about home, family, the private base of operations, whatever A actually built that house to mean. B's Venus sitting in it says something about the flavor B brings into that domain when B is around - not that B and A have any particular aspect between them, not that anything is "activated" in the sense of triggering an event. It is closer to noticing which room someone tends to occupy at a gathering than to noticing what they said to you.

This is why a full synastry picture wants both layers read together but never merged. The aspect grid is about the relationship between the two people's planetary functions. The overlay grid is about where each person's expression settles inside the other person's lived structure. You can have a loaded aspect grid and a quiet overlay, or the reverse.

The scan: houses are not evenly loaded, and that's fine

Across 600 pairs, 7200 overlay placements were counted. The busiest houses were house 3 at 9.0%, house 9 at 8.9%, house 10 at 8.8%, house 2 at 8.5%, house 8 at 8.4%. If houses were all identical wedges you'd expect each one to draw close to one twelfth of the placements, which is about 8.3%. What you actually see is a tight cluster hovering just above and around that mark - nothing dramatic, nothing that should make you sit up when your partner's Mars happens to fall in your third house. Houses are not equal in angular width; some are naturally wider than others depending on the latitude and time of birth involved, and a wider house catches more passing planets across a population of charts purely by having more sky to catch them in. That is the whole explanation for why house 3 edges out house 8 in this sample. It is not that the third house is somehow more "popular" as a destination for meaning. It is geometry doing what geometry does.

The practical takeaway: an overlay landing in a particular house is common, not rare, and its mere occurrence is not a message. What matters is which house it is, for your actual two charts, and what that house has meant across the rest of the reading - not whether the placement itself is statistically unusual, because none of them really are.

Why it needs a birth time, and why the engine won't fake one

Houses depend on the exact minute and the exact place of birth. Move the clock by twenty minutes and a house cusp can shift enough to move a planet from one house to the next, changing the entire overlay reading for that planet. This is not a rounding error the way a Sun sign can survive a fuzzy birth date - it is structural. Without a real birth time, the engine returns the aspect grid and simply omits the overlay section rather than quietly defaulting to noon or some other placeholder. A guessed birth time produces a house overlay that looks exactly as confident and specific as a real one, and there is no way to tell the difference by looking at the output - which is exactly why guessing is worse than leaving it blank. If you don't have a birth time, you get aspects only, and that is the honest result.

The worked pair, house by house

Person A was born 13 July 1973 at 06:52 in Singapore. Person B was born 9 December 1996 at 12:21 in Penang. Both birth times are known, so both overlay directions are printed - B's planets in A's houses, and separately, A's planets in B's houses, because these are not mirror images of each other.

B's Sun falls in A's house 5 (Sagittarius 17°23'), and B's Moon falls in A's house 5 as well (Scorpio 27°19') - both lights landing in the same house of A's chart, the house of personal creative expression and pleasure, for what that is worth as one data point among many. B's Mercury falls in A's house 6 (Capricorn 6°27'), B's Venus in A's house 4 (Scorpio 19°58'), B's Mars in A's house 3 (Virgo 20°14'). Moving outward: B's Jupiter falls in A's house 7 (Capricorn 20°03'), B's Saturn in A's house 9 (Aries 0°38'), B's Uranus in A's house 7 (Aquarius 2°06'), B's Neptune also in A's house 7 (Capricorn 26°03') - three outer points converging on A's seventh house, the house most traditionally tied to partnership, is a genuine cluster worth noting as a cluster, not as an omen. B's Pluto falls in A's house 5 (Sagittarius 3°33'). B's North Node falls in A's house 3 (Libra 5°18'), and by construction B's South Node falls opposite it, in A's house 9 (Aries 5°18').

Running the other direction: A's Sun falls in B's house 5 (Cancer 20°25'), A's Moon in B's house 10 (Sagittarius 22°41'), A's Mercury in B's house 6 (Leo 1°52'), A's Venus also in B's house 6 (Leo 15°18'). A's Mars falls in B's house 2 (Aries 13°54'). A's Jupiter falls in B's house 12 (Aquarius 9°24'), A's Saturn in B's house 4 (Gemini 27°39'), A's Uranus in B's house 8 (Libra 19°03'), A's Neptune in B's house 9 (Sagittarius 4°58'), A's Pluto in B's house 7 (Libra 1°56'). A's North Node falls in B's house 11 (Capricorn 7°42'), and A's South Node falls in B's house 5 (Cancer 7°42').

Notice the asymmetry. B's lights cluster in A's fifth house; A's Moon sits alone in B's tenth. B has three outer planets stacking in A's seventh house of partnership; A has no comparable stack anywhere in B's chart - A's outer planets are scattered across the fourth, eighth, ninth and twelfth. This is normal. There is no rule requiring two charts to distribute their overlays symmetrically, and reading a false symmetry into a chart where none exists is a common way to over-claim.

What the aspect count actually tells you, and what it doesn't

It helps to know the baseline before treating any single contact as significant. A scan of 600 real pairs, built from a pool of 200 charts, found an average of 50.49 contacts between two charts, ranging from as few as 29 to as many as 72. Of those, an average of 36.99 are major aspects, and 14.1 link two personal bodies - Sun, Moon, Mercury, Venus, Mars, Ascendant, Midheaven. The average number of harmonious contacts is 15.91, tense contacts 25.41, and contacts exact within one degree average 17.28.

The point most readers miss when they open a synastry report for the first time: two random strangers, pulled from a pool with no connection to each other, already share about fifty contacts on average. A long list is not evidence of a bond. It is what geometry does when you put two wheels of the zodiac next to each other and start measuring angles - degrees add up to contacts whether the two people have ever met or not.

Against that background, person A and person B show 57 contacts between them, 40 major, 19 personal to personal, 19 harmonious, 30 tense, 18 exact within one degree, and 9 double whammies - meaning nine pairs of planets that are in aspect in both directions at once. That is a count modestly above the 50.49 average and with more tense contacts (30) than harmonious ones (19), which is itself unremarkable - the population average already runs tense-heavy, at 25.41 versus 15.91. None of these numbers add up to a verdict. They describe a texture: where the pressure sits, where the ease sits, and how much of the chart is talking to the other chart at all.

No score, and why that's deliberate

There is no compatibility percentage anywhere in this report, and there will not be one. Adding a Venus trine to a Saturn square into a single number requires a weighting scheme - how much is a trine worth against a square, does an exact orb count double, does an outer planet matter as much as a personal one - and no two astrologers agree on that weighting, because there isn't a physical or logical fact that settles it. Any score you've seen elsewhere is one person's opinion dressed up as arithmetic. This report gives you the counts raw: how many contacts, how many major, how many harmonious, how many tense, how many exact, how many double whammies, and where each planet lands house-wise if a birth time is available. The reading is left to the contacts themselves, read one at a time, in the voice of the person doing the reading - not compressed into a single figure that can't actually carry the weight put on it.

One more thing the grid will never tell you, because it isn't a real question in synastry: whether a contact is applying or separating. That distinction belongs to a single chart, where all the planets are moving through one continuous stretch of time and an aspect is either closing in or pulling apart. Two natal charts are two different moments entirely - there is no shared clock for an aspect between them to be closing against, so nothing here is "approaching" or "fading." Each contact simply is, exact to whatever orb is printed, for as long as both people are alive to carry the placements that make it.

Where to run your own two charts

If you want to see your own overlay pattern rather than someone else's, the calculator is at https://spacemirror.ru/en/synastry.html. It needs a birth date, time and place for both people - the time matters for the overlay section specifically, and if you don't have it, you'll still get the full aspect grid, just without the houses. Go in expecting fifty-odd contacts as the normal range, not the exception, and read the cluster in your own chart the way you'd read the cluster above: as a place where attention gathers, not as a prediction of where the relationship goes.