Synastry

Two charts, one wheel

Enter two sets of birth details to see where one person's planets fall in the other's chart. The wheel inside is one person's natal chart, drawn exactly as the birth chart page draws it; the ring around it is the other person's planets, placed against those signs and houses.

Only used to label the chart on this page.

Local clock time as recorded. Without it the rising sign and every house placement is guesswork — the planets by sign would still be right.

Only used to label the chart on this page.

Local clock time as recorded. Without it the rising sign and every house placement is guesswork — the planets by sign would still be right.

Both charts are worked out in your browser. Your dates, times and cities stay there — they are not sent anywhere, kept after you close the page, or put in the address bar. Choosing a birth country downloads that country's city list, so we can tell a country was picked and nothing else.

How to read a bi-wheel

  • The inner wheel is one person's natal chart: their signs, their houses, their planets.
  • The outer ring is the other person's planets, plus their Ascendant (AC) and Midheaven (MC), placed at the degree they occupy in the inner person's chart.
  • Reading a planet outwards tells you which of the inner person's houses it falls in. Swap to read it the other way round — synastry is not symmetrical, and both views are true.

One chart at a time is the birth chart calculator; for sun-sign compatibility without birth times, see compatibility.

Questions

Whose chart is the wheel?
The person named "inside". Their signs and houses frame the picture, and the other person's planets are laid around it. Swapping redraws the whole thing from the other point of view, which is a different — and equally valid — reading.
Why are there no lines between the two charts?
Those lines are cross-aspects, and naming them is a separate piece of work with its own sourcing. This page draws the picture the aspects are read from; it does not interpret it.
Are the birth details sent anywhere?
Both charts are calculated in your browser, nothing is stored, and nothing is put in the address bar — so there is no link that carries anyone's birth details, and reloading starts over. One thing does reach us: picking a birth country downloads that country's city list, so the request shows a country was chosen. The dates, the times and the cities themselves never leave your browser.
Do I need both birth times?
Yes. Houses and the rising sign depend on the time, and the whole point of a bi-wheel is where one person's planets fall in the other's houses. Without a reliable time for the person on the inside, the houses it shows would be guesswork.