Free Self-Discovery Tool
Free synastry house overlays calculator: which of your houses their Sun, Moon, Venus, Mars, Saturn and Pluto fall into, which of their houses yours fall into, and the tightest cross-chart aspects.
Start with the house: it names the arena of your life the other person walks into. Then the planet: the Sun is who they are, the Moon what they need, Venus how they love, Mars what they want, Saturn what they hold you to, Pluto what they change in you. Their Moon in your 4th house is their feelings living in your home and family; their Mars in your 10th is their drive pushing your career. The calculator computes every overlay from the two charts and links each of the six lead placements to its full write-up.
An overlay is never symmetrical: their Sun in your 7th does not put your Sun in their 7th. The calculator shows where you land in their houses too, and where the two charts concentrate, the house of yours that receives the most of their planets. Beneath the overlays it lists the tightest aspects between the two charts within four degrees, because the overlay says where the contact lands and the aspect says how it behaves.
It is where one person’s planet falls in the other person’s houses. Their Sun in your 7th house means the degree of their Sun lies inside your 7th house, so their identity lands in your partnership arena. Overlays run both directions and the calculator shows both.
The Sun (their identity), Moon (their feelings and needs), Venus (their affection), Mars (their drive), Saturn (their weight and commitment) and Pluto (their intensity). The calculator leads with those six and shows the other four in the full table.
Overlays need the house person’s birth time: to place their planets in your houses the calculator needs your time, and to place yours in theirs it needs theirs. With one time missing it shows the direction it can compute and says so.
It is the classic partnership overlay: you tend to see them as a partner and they feel most themselves in a committed pairing with you. It says where they land, not whether they should stay; every house has a gift and a shadow, and the page for each overlay says both.
Each chart’s own cusps in the system the birth chart was cast with (Placidus by default). A planet within a degree of a cusp can sit in the neighbouring house in another system, and the result says so where it applies.