☽ Free Moon Sign Compatibility Calculator
MODERNA modern technique: twentieth-century astrology.
Umbriel's free Moon compatibility calculator compares two Moons: their signs, exact degrees, the aspect between them and where each falls in the other's chart. No account, no email. It works from the real positions, not from sign pairs, so a Moon at 1° and a Moon at 29° of the same sign are not treated as identical.
- What you'll needBoth people's birth dates (times for the houses)
- What you getBoth Moons with exact degrees, the aspect between them, and where each Moon falls in the other's chart
- CostFree, no account required
Runs in your browser.
4420+ people cast their chart here in the last 30 days.
What Moon compatibility is
Of all the comparisons people make between two charts, the Moon is the one most astrologers would keep if they could only keep one. The Sun describes what someone is aiming at; the Moon describes what they need in order to be comfortable, sleep, food, mess, quiet, reassurance, the shape of an ordinary evening. Two people can admire each other's Suns and still find the daily rhythm hard, and that is usually a Moon conversation.
Sign-pair compatibility tables are where this goes wrong. They treat every Cancer Moon as the same Cancer Moon, when what matters is the aspect between the two Moons and how tight it is. Two Moons in trine at half a degree behave like one instrument; the same trine at eight degrees is barely audible. And two Moons in the same sign at opposite ends of it are not conjunct at all.
The other half is placement. Where your Moon falls in their houses, and theirs in yours, describes the area of life each person's needs land in for the other. It is often more recognisable than the aspect, and it is the part that needs both birth times. Umbriel gives the degrees, the aspect with its orb and the overlays, and the full comparison adds an overall score out of 100 that summarises the aspect list.
How Umbriel computes it
This tool compares the two people's Moons inside a full chart-to-chart comparison. Each birth is cast as an ordinary natal chart, and every planet of one chart is laid against every planet of the other, so the Moon-to-Moon aspect appears alongside the Moon's contacts to the other person's Sun, Venus, Saturn and the rest. An aspect is counted when the gap between two longitudes is within its orb of 0, 60, 90, 120 or 180 degrees. The default orbs are 8 degrees for conjunction and opposition, 7 for trine and square and 5 for sextile, with 2 degrees more for aspects involving the Sun or Moon, and each contact is listed with its exact orb, so a Moon at 1 degree and a Moon at 29 degrees of one sign are compared by their real distance and not by sign. Each person's planets are also placed into the other person's houses, using the house system chosen for that chart. The Moon positions come from the same engine as every chart on this site, checked against NASA/JPL Horizons to 0.27 arcminutes over 1600 to 2050. Birth time matters in two ways: the house overlays need it, and without it the tool says there are no houses to place planets in. The Moon moves about half a degree an hour, so an unknown time can leave a Moon several degrees out, or in the neighbouring sign. The full comparison also prints an overall score out of 100 built from the cross-aspects; that number summarises the aspect list and is not a measurement, and compatibility itself is a symbolic reading laid over real positions.
What's in your result
- Both Moons, to the degreeSign and exact degree for each, so near-cusp Moons are visible.
- The aspect between themNamed, with its exact orb. The number that decides how loud it is.
- Each Moon in the other's housesWhere each person's needs show up for the other. Needs both birth times.
- Moon phase and elementEach Moon's phase at birth and the element pairing, as a lighter second reading.
- Moon to the other's Sun, Venus and SaturnThe contacts that most often describe how the two settle together.
- The full synastry alongsideThe Moon comparison sits inside the complete chart comparison if you want the rest.
Common questions
What is Moon sign compatibility?
Comparing the Moon in two birth charts: the aspect between them and where each falls in the other's chart. The Moon is traditionally read for emotional needs and daily rhythm, which is why it is often considered the most telling single comparison.
Are the same Moon signs the most compatible?
Not automatically. Two Moons in the same sign are only conjunct if they are close in degree. One at 2° and one at 27° of the same sign are almost thirty degrees apart. Sameness is also not the only thing that works; complementary Moons often describe an easier daily life than identical ones.
Do we both need birth times?
For the Moon signs and the aspect between them, usually not, though a Moon can change sign within a day, so a birth close to an ingress does need a time. For the house overlays, yes, both times.
Is the Moon more important than the Sun for compatibility?
Many astrologers think so, and the reasoning is practical, not mystical: the Sun describes what someone is reaching for, the Moon what they need to be comfortable, and living together is mostly the second thing. It is a view worth testing against your own experience rather than accepting.
Is the Moon compatibility calculator free?
Yes, both Moons, the aspect with its orb, and the overlays, with no account and no email.
Do I need an account or an email address?
No. There is no sign-up, no email capture and no free trial. Enter your details and the result is drawn in your own browser.
Go deeper
Every one of these is a page in its own right, written out one at a time.
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Umbriel offers every system here as a set of prompts to think with, never as a statement of fact about who you are. Take what's useful, leave the rest.