Black Moon Lilith turns up in birth chart readings, compatibility posts and horoscope apps, often with confident descriptions and very little explanation of what is being measured. Two sites give the same birthday two different Lilith signs. One calls it a planet, another an asteroid, a third a hypothetical moon. Most never say which of those they mean.
This guide separates the astronomy from the astrology. It explains what Black Moon Lilith is as a point in space, how it is computed from the Moon's orbit, why "mean" and "true" Lilith disagree, how fast it moves, and what the astrological tradition reads into it. The examples use the Toolz Lilith sign calculator, and every position quoted was worked through with the formula shown below.
TL;DR: Black Moon Lilith is not a body. It is the apogee of the Moon's orbit, the point where the Moon is farthest from Earth, which lines up with the empty second focus of the Moon's elliptical path. Mean Lilith, the default in most astrology software, uses the averaged motion of that apogee and moves about one degree every nine days, so it stays roughly nine months in each sign and circles the zodiac in about 8.85 years. True or osculating Lilith follows the wobbling apogee of the moment and can sit more than thirty degrees away. Astrology reads Lilith's sign as a suppressed or rejected part of the self; that is tradition, not science. The Black Moon Lilith calculator reports mean Lilith to the arcminute from a birth date, client-side, free, no signup.
What is Black Moon Lilith, astronomically?
Black Moon Lilith is the lunar apogee: the point on the Moon's orbit where it is farthest from Earth. The Moon's orbit is an ellipse, not a circle, with Earth at one focus. The other focus is empty, and seen from Earth it lies in the same direction as the apogee. Astrology marks that direction on the zodiac and calls it Black Moon Lilith.
The difference between the near and far ends of the orbit is real and measurable. NASA's Moon fact sheet lists a perigee distance of about 363,300 km and an apogee of about 405,500 km. It also lists the period in which the line joining perigee and apogee, the line of apsides, turns once around the sky: about 3,232.6 days, or roughly 8.85 years. That slow rotation is exactly what Mean Lilith tracks.
Nothing sits at the apogee point. There is no object to observe, which is why Lilith is described as a calculated or sensitive point, in the same class as the lunar nodes.
Why do different sites give different Lilith signs?
Because at least four different things are called "Lilith", and most sites do not say which one they use.
| Name | What it is | How it moves | Relation to this calculator |
|---|---|---|---|
| Mean Black Moon Lilith | Averaged position of the lunar apogee | Smooth, about 40.7 degrees a year | This is what the Toolz calculator reports |
| True or osculating Lilith | Apogee of the instantaneous orbit at that moment | Wobbles, can swing tens of degrees within a month | Different point, often a different sign |
| Asteroid 1181 Lilith | A real minor planet in the asteroid belt | Its own orbit around the Sun | Unrelated object |
| Dark Moon Lilith | A proposed second moon of Earth | Never confirmed to exist | Not calculated here |
Mean and true Lilith are the pair that trips people up most, because both are called Black Moon Lilith. The true apogee is disturbed by the Sun's gravity, so the osculating ellipse that best fits the Moon's motion at a given instant keeps changing shape and orientation. Its apogee can differ from the mean by more than thirty degrees over a single month. That is not a refinement of the mean position; it is a different point, often in a neighboring sign. Some software also offers a smoothed "interpolated" apogee between the two.
If a reading elsewhere disagrees with this calculator, the first thing to check is whether it uses mean or true Lilith. The second is whether it means the asteroid.
How is mean Black Moon Lilith calculated?
Mean Lilith falls straight out of two of the Moon's mean orbital elements, the same ones any lunar position calculation already needs. The Toolz astrology engine takes its formulas from Jean Meeus, Astronomical Algorithms (2nd edition, chapter 47).
The mean perigee is the Moon's mean longitude minus its mean anomaly. The mean apogee is the mean perigee turned half a circle:
L' = 218.3164477 + 481267.88123421 T (Moon's mean longitude, degrees)
M' = 134.9633964 + 477198.8675055 T (Moon's mean anomaly, degrees)
Mean Lilith = L' - M' + 180
= 263.3530513 + 4069.0137287 T (mod 360)
T = (Julian Day - 2451545.0) / 36525 (centuries from 1 Jan 2000, 12:00 TT)
The formula also includes very small squared and cubed terms in T, which change the result by far less than an arcminute for modern birth dates.
Worked example: 3 March 1995
- Julian Day for 3 March 1995 at 12:00 is 2,449,780.0.
- T = (2,449,780.0 - 2,451,545.0) / 36,525 = -1,765 / 36,525 = -0.048323.
- 4,069.0137 x -0.048323 = -196.627.
- 263.3531 - 196.627 = 66.726 degrees.
- The zodiac starts at 0 degrees Aries, and Gemini covers 60 to 90 degrees, so 66.726 is 6.726 degrees into Gemini.
- 0.726 of a degree is 43.6 arcminutes.
Result: Black Moon Lilith at about 6 degrees 44 minutes Gemini, which is what the calculator shows for that date with no birth time. Entering a birth time of 09:15 in London moves the moment about three hours earlier than noon and the result to 6 degrees 43 minutes Gemini, a one-arcminute difference.
How long was Lilith in Gemini that year?
The same formula tells you. Mean Lilith moves 4,069.0137 degrees per century, which is 0.1114 degrees per day. From 66.73 degrees on 3 March, reaching 60 degrees (the start of Gemini) took about 60 days, and reaching 90 degrees (the end) takes about 209 days. So mean Lilith was in Gemini from roughly the start of January 1995 to roughly the end of September 1995, about nine months, which is the typical stay.
How fast does Black Moon Lilith move?
| Measure | Value | Where it comes from |
|---|---|---|
| Daily motion | About 0.111 degrees | 4,069.0137 / 36,525 |
| Time to move one degree | About 9 days | 1 / 0.1114 |
| Time in one sign | About 8.9 months | 30 degrees / 40.69 degrees per year |
| Full circuit of the zodiac | About 8.85 years | 360 / 40.69, matching NASA's apsides period |
In practice that makes Lilith a semi-generational placement. People born within a few months of each other usually share a Lilith sign, and people born nine years apart often do too. It moves far faster than Chiron or the outer planets and far slower than the Moon itself.
Do you need a birth time for your Lilith sign?
Usually not. At nine months per sign, the date settles the sign on all but a handful of days a year, the days when Lilith crossed from one sign into the next. On those days the calculator flags the boundary and shows the uncertainty rather than silently picking one.
A birth time and a birth place do add one thing: the house. With both, the calculator also reports which house Lilith falls in, using the Placidus house system, the default in most modern software. Inside the polar circles, where Placidus cannot be computed, it switches to equal houses. A time without a place is not enough: the time is read as UTC and the House field stays empty.
In the 3 March 1995 example, adding 09:15 and London places Lilith in the 1st house, just past a Placidus ascendant at 28 degrees 30 minutes Taurus. Under whole-sign houses, where the entire rising sign is the 1st house, the same Lilith in Gemini would fall in the 2nd. House systems genuinely disagree like this, which is one reason to know which one a reading uses. If you read charts in whole-sign houses, the birth chart calculator offers that system.
What does Lilith mean in astrology?
This is where astronomy ends and interpretation begins. Everything in this section is traditional astrological attribution: cultural material with a long history, not a measured effect. Controlled tests of astrology, such as the double-blind study Shawn Carlson published in Nature in 1985, have not found that charts predict personality, and the calculator's own results say plainly that readings are for interest and entertainment.
Within the tradition, the name comes from Lilith in Jewish folklore, a figure who refused to submit and was written out of the story. Astrologers read the Black Moon Lilith placement in that light: the part of yourself you were taught to hide or were punished for, such as an appetite, an anger or a refusal, and what happens when it comes out anyway. The sign is read as the style of that suppressed material, and the house as the area of life where it shows up.
Here is the reference table the calculator's results are built on. Degrees are ecliptic longitude in the tropical zodiac.
| Sign | Longitude | Element | Modality |
|---|---|---|---|
| Aries | 0 to 30 | Fire | Cardinal |
| Taurus | 30 to 60 | Earth | Fixed |
| Gemini | 60 to 90 | Air | Mutable |
| Cancer | 90 to 120 | Water | Cardinal |
| Leo | 120 to 150 | Fire | Fixed |
| Virgo | 150 to 180 | Earth | Mutable |
| Libra | 180 to 210 | Air | Cardinal |
| Scorpio | 210 to 240 | Water | Fixed |
| Sagittarius | 240 to 270 | Fire | Mutable |
| Capricorn | 270 to 300 | Earth | Cardinal |
| Aquarius | 300 to 330 | Air | Fixed |
| Pisces | 330 to 360 | Water | Mutable |
With a longitude of 66.73 degrees, the 1995 example lands in Gemini, an Air sign of Mutable modality. The result card lists the sign, the degree, element, modality, traditional ruler, the house when available, and a short reading of the placement.
How to find your Lilith sign, step by step
- Open the free Lilith sign calculator.
- Enter your birth date. This alone gives the sign and degree on nearly every date.
- If you want the house, add your birth time and pick your birth city. Both are needed.
- Click "Find my Lilith sign".
- Read the sign, degree, element, modality and house. If a boundary notice appears, your birth fell on a day Lilith changed sign, and your birth time decides it.
- Use Copy to save a plain-text summary that includes the UTC instant the chart was cast for.
Is my birth information stored?
No. The calculation runs client-side in your browser, in JavaScript, and nothing you type is sent, logged or saved. Once the page has loaded it keeps working with the network turned off.
What mistakes should you watch for?
| Problem | What is going on | What to do |
|---|---|---|
| Another site shows a different sign | It likely uses true or osculating Lilith, or the asteroid | Check which point it calculates |
| House field is empty | No birth time, or a time without a place | Enter both time and city |
| House differs from another chart | Different house system, such as whole-sign vs Placidus | Compare using the same system |
| Sign flagged as uncertain | Birth on a day Lilith changed sign | Add the birth time to resolve it |
| Time entered without a city | A time with no place is read as UTC | Pick the birth city so the time is read as local time |
| Treating the result as a prediction | Lilith readings are tradition, not measurement | Read it as reflection, not advice |
Lilith compared with other calculated points
Lilith belongs to a family of points derived from orbits or chart geometry rather than bodies you can see.
| Point | Defined by | Cycle | Calculator |
|---|---|---|---|
| Black Moon Lilith (mean) | Lunar apogee | About 8.85 years, forward through the signs | Lilith sign |
| North Node (mean) | Where the Moon's orbit crosses the ecliptic heading north | About 18.6 years, backward through the signs | North Node calculator |
| Part of Fortune | Ascendant plus Moon minus Sun (by day) | Depends on birth time | Part of Fortune calculator |
| Chiron | A real small body between Saturn and Uranus | About 50 years | Chiron sign calculator |
The nodes and Lilith both come from the Moon's orbit, which is why the Toolz engine derives them from the same mean elements rather than from separate tables that could drift apart.
Alternatives for finding Black Moon Lilith
Desktop astrology programs and ephemeris-based chart sites all offer Lilith, and most can switch between mean and true. When you compare, set both to the same variant, the tropical zodiac, and the same house system; then results for the mean point should agree closely, usually to within an arcminute or two. A larger gap almost always means one side is set to true Lilith.
For the full astrology set on Toolz, including the Sun, Moon and rising calculators and synastry, see the astrology tools hub. To look up your own placement, calculate your Black Moon Lilith from your birth date.
