Your date of birth is enough — the time and place refine the result. Enter them on the Birth chart page: it calculates the Moon, Venus, Mars and the other planets, with the ascendant if the time is known, then come back here to read what tradition makes of them.
When you say “I’m a Scorpio”, you are talking about the Sun’s position on the day you were born. It is the easiest piece of information to know — the date is enough — which is why horoscopes make do with it. But within astrological reasoning itself, the Sun describes identity and will, not the way one loves. For couples, astrologers look first at three other points of the chart: the Moon, which describes emotional needs and what reassures; Venus, which describes how one attracts, loves and what one finds beautiful; Mars, which describes desire, drive and the way one quarrels. Two Scorpios can have very different Moons, Venuses and Marses — and that is where sign portraits most often go wrong.
The Birth chart page calculates these positions for your date, time and place of birth. This page explains how tradition reads them in love, then how two charts are compared: that is synastry.
The Moon changes sign every two and a half days; two people born in the same week can therefore have opposite Moons. Tradition reads in it emotional childhood, the way one reacts under the sway of emotion, and above all what one needs from the other when things go badly. It is the point of the chart astrologers look at first for life together, because it describes daily life more than seduction.
The Moon in the sky — its phases, its twenty-nine-and-a-half-day cycle, what science says about it — has its own page: The cycles of the Moon. Here we are talking about the natal Moon, the one in your chart.
Venus describes what one finds desirable, how one approaches the other and how one shows attachment. It never strays more than two signs from the Sun: your Venus is therefore in your Sun sign or in one of the two signs before or after it. Tradition has it turn retrograde for forty days every eighteen months, a period reputed favourable to the return of old loves and unfavourable to new commitments — a belief, not a calendar.
Mars describes the way one wants and fights: how one takes the initiative, expresses desire, gets angry. By element, tradition distinguishes four families.
The classic couple reading crosses one partner’s Venus with the other’s Mars: is what one finds beautiful what the other expresses spontaneously? It is the first comparison synastry makes.
Synastry superimposes two charts and looks at how the planets of one “aspect” those of the other. Aspects are angles: the conjunction (0°) merges, the trine (120°) and sextile (60°) ease, the square (90°) chafes and pushes to act, the opposition (180°) confronts and asks for balance. Astrologers allow a tolerance of a few degrees. Here are the comparisons tradition finds most telling, in the order to look at them:
To do it yourself: calculate both birth charts, note each person’s Moon, Venus and Mars sign, and compare the elements — same or compatible elements (Fire and Air, Earth and Water) on one side, elements that chafe on the other. The Love compatibility page does this work for two dates of birth and adds it to the site’s other readings.
Nothing demonstrated. Studies that looked for a link between two people’s planetary positions and the length of their union — including marriage registers of hundreds of thousands of couples — found nothing, and astrologers themselves predict no better than chance when tested blind. But synastry has a quality that sign horoscopes lack: it forces you to describe two people, with their needs, their way of loving and their way of getting angry, and to ask how these things fit together. Done as a pair, that reading is a good conversation about what each expects when things go badly, what one finds beautiful in the other and how one argues. The conversation is real; the sky has nothing to do with it.
For what tradition ascribes to each sign in love, without going through the Moon and Venus, see Love sign by sign; for two other traditions that match couples, the Chinese zodiac and Vedic astrology.
For Venus and Mars, no: they move at most a degree a day. For the Moon it helps: the Moon covers twelve to fifteen degrees a day and changes sign every two and a half days; without the time, the calculation can pick the wrong sign if you were born on a day of change — the calculator flags it.
In tradition it is the relationship that asks the most daily effort, because two ways of being reassured get in each other’s way: one wants to talk when the other wants silence, one wants to go out when the other wants to stay in. Nothing insurmountable — simply something to know about each other.
It is a widespread astrological belief, not an observation. Venus is retrograde for about forty days every eighteen months; couples formed during those periods last neither more nor less than others.
Page checked in September 2026. The data cited can change.
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