Compatibility calculator
Sun signs only get you so far. Put two birth dates (and times, if you have them) side by side and see how the two charts actually meet: where Venus, Mars and the Moon of one touch the other.
- Both big threesSun, Moon and Rising sign for each of you (Rising with a birth time).
- Your Sun-sign pairThe classic pairing, with a link to the full page on it.
- Venus, Mars, Moon contactsEvery aspect between the two charts that involves Venus, Mars or the Moon, tightest first.
- A plain summaryCounted from the aspects, not written by AI: where it flows and where it asks for work.
How it’s calculated
Comparing two charts is called synastry. We calculate both natal charts from your dates, times and cities (with each city’s historical time zone), then measure the angles between one person’s planets and the other’s.
We keep the contacts astrologers look at first in a relationship: anything that involves Venus (affection and taste), Mars (desire and drive) or the Moon (feelings and comfort), met by the other person’s Sun, Moon, Mercury, Venus, Mars or Rising sign. Orbs are the same as in a single chart: 8° for conjunctions and oppositions, 7° for trines and squares, 5° for sextiles, two degrees more when the Sun or Moon is involved.
The summary is counted, not invented: how many contacts flow (trines, sextiles), how many create tension (squares, oppositions), how many fuse (conjunctions), and whether the classic pairings are there: Venus with Mars, the Sun with the Moon, Moon with Moon. No score out of 100; real relationships are more than a number.
Asked often
How accurate is a compatibility calculator?
The positions are exact; we compute them for each birth minute and city. What no calculator can do is tell you whether a relationship will work: aspects describe dynamics, and people with “difficult” synastry build good lives together all the time. Read the result as a map of where things come easily and where they take attention.
What if we don’t know our birth times?
Leave the time out. We calculate for noon and skip the Rising sign for that person. The Sun, Venus and Mars hardly move in a day, so most contacts stay the same; only a Moon contact near the edge of its orb can come or go.
Why Venus, Mars and the Moon?
They are the planets of relating: Venus is affection and what attracts us, Mars is desire and how we act, the Moon is feeling, comfort and daily rhythm. When one person’s Venus or Moon touches the other’s chart, it is felt in everyday life.
Is a square or opposition bad?
No. Squares and oppositions bring friction, and friction is also chemistry: many lasting couples have several. Trines and sextiles are easy, sometimes so easy they go unnoticed. A mix is the most common pattern of all.
How is this different from Sun-sign compatibility?
Sun-sign compatibility compares one point per person: twelve signs, 78 pairs. Synastry compares whole charts, so two Leo–Scorpio couples can look very different. The Sun-sign pair is shown too, with a link to the full page about it.
Two charts, read together
The compatibility report reads every aspect between the two charts in plain language: where you click, where it takes work, and how to meet each other there. The couple book goes further, with chapters for each of you.
Other free calculators
- Personal horoscopeYour transits for the next 30 days
- Venus sign calculatorLove style and taste, from your birth date
- Mars sign calculatorDrive, desire and temper, from your birth date
- Mercury sign calculatorHow you think and talk, from your birth date
- Birth chart calculatorCalculate your birth chart
- Moon sign calculatorFind your Moon sign
- Rising sign calculatorFind your Rising sign
- Sky calendarCalendars by year: 2026–2028
- Planets in the signsTen planets, twelve signs: the full guide