Synastry chart calculator
Every planet of one chart against every planet of the other.
The first birth's planets down the side, the second's across the top.
| Sun | Moon | Mercury | Venus | Mars | Jupiter | Saturn | Uranus | Neptune | Pluto | |
|---|---|---|---|---|---|---|---|---|---|---|
| Sun | square, 3.3 degrees from exact | conjunction, 0.7 degrees from exact | sextile, 2.8 degrees from exact | square, 4.9 degrees from exact | square, 5.1 degrees from exact | |||||
| Moon | trine, 5.8 degrees from exact | sextile, 2.3 degrees from exact | sextile, 2.5 degrees from exact | |||||||
| Mercury | trine, 8.6 degrees from exact | square, 1.2 degrees from exact | square, 5.0 degrees from exact | conjunction, 5.1 degrees from exact | ||||||
| Venus | conjunction, 3.9 degrees from exact | trine, 5.9 degrees from exact | square, 1.7 degrees from exact | |||||||
| Mars | trine, 5.7 degrees from exact | |||||||||
| Jupiter | conjunction, 9.2 degrees from exact | opposition, 2.9 degrees from exact | opposition, 2.7 degrees from exact | opposition, 7.5 degrees from exact | ||||||
| Saturn | sextile, 1.0 degrees from exact | trine, 3.1 degrees from exact | ||||||||
| Uranus | opposition, 1.3 degrees from exact | conjunction, 0.4 degrees from exact | sextile, 0.7 degrees from exact | |||||||
| Neptune | opposition, 3.8 degrees from exact | conjunction, 5.5 degrees from exact | sextile, 4.4 degrees from exact | |||||||
| Pluto | trine, 7.2 degrees from exact | square, 5.6 degrees from exact | trine, 6.6 degrees from exact | conjunction, 7.8 degrees from exact |
- conjunction, 0°, orb 8
- sextile, 60°, orb 6
- square, 90°, orb 7
- trine, 120°, orb 8
- opposition, 180°, orb 8
Each orb is 2 wider when the Sun or the Moon is one of the pair: the house's aspect engine's orbs, the birth chart's. The number in a cell is how many degrees the angle stands from exact, darker within 1 degree.
How to read the grid
Each row of the grid is a planet of the first chart and each column a planet of the second. Where a row meets a column, the cell holds the aspect the two planets make, if they make one, and its orb: how many degrees the angle stands from exact, to a tenth. An empty cell means no aspect within the orbs; a hatched one depends on a birth hour that was not given.
Every position comes from the ephemeris (Meeus), read for each birth's minute in the time zone of its place. The orbs listed under the grid are the house's aspect engine's, the same the birth chart calculator draws.
To compare the same two births by their signs, across the seven planets the house reads as generations, see the compatibility calculator.
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Conjunction. Two planets on nearly the same degree: astrology reads a conjunction as the two acting as one.
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Sextile. Two planets 60 degrees apart, a sixth of the circle: astrology reads a sextile as an easy opening between the two.
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Square. Two planets 90 degrees apart, a quarter of the circle: astrology reads a square as friction between the two, the aspect of strain and effort.
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Trine. Two planets 120 degrees apart, a third of the circle: astrology reads a trine as the easiest of the five, the two running together.
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Opposition. Two planets 180 degrees apart, facing across the circle: astrology reads an opposition as the two pulling against each other.
written: what astrology reads in each aspect, the same for any two charts that form it; not a verdict on two people
About this tool
What does this synastry chart calculator show?
This free synastry chart calculator sets two birth charts against each other and finds every aspect between one chart's planets and the other's: conjunction, sextile, square, trine and opposition, each with its orb. The first chart's ten planets run down the side of the grid and the second chart's across the top. The positions come from the ephemeris, Jean Meeus's public-domain algorithms.
How is it different from the compatibility calculator?
This page measures angles: where each planet of one chart stands against each planet of the other, with no score and no verdict. The compatibility calculator compares the two births' signs across the seven planets the house reads as generations, by its element matrix, and ends with a figure.
Which orbs does it use?
The orbs of the house's aspect engine for a birth chart, the same the birth chart calculator draws: 8 degrees for the conjunction, the opposition and the trine, 7 for the square and 6 for the sextile, with 2 more when the Sun or the Moon is one of the pair. A cell holds the one aspect its angle falls within.
What if a birth time is unknown?
Choose that it is not known. That person's planets are then read across the whole local day. The slow planets barely move in a day, so their aspects hold all day and print the widest their orb came; the Moon moves about 12 to 15 degrees in a day, so an aspect of that Moon that depends on the hour is left out and its cell is hatched.
Why does the place matter?
The place sets the time zone, which turns a clock time into the instant the planets are read for. Without a time it sets which 24 hours count as the birth day; with no place the day is read in UTC, and the page says so.
How accurate is it?
The house checks Meeus's algorithms against JPL's ephemeris: every planet within about a tenth of a degree from 1900 to 2050. Orbs are a convention, and other programs draw them wider or narrower, so an aspect near the edge of its orb can appear in one program and not in another.