Moon Phase Compatibility: What the TikTok Trend Means and How to Find Yours

Moon phase compatibility is a TikTok trend in which two people look up the lunar phase on their birthdays and check whether the two phases, drawn next to each other, fit together to form a complete full moon. The hashtag has crossed 430 million views since the test went viral in 2023, which is why a 200-year-old planning publication keeps getting asked about it. Below is what the test actually is, how to find your own birth phase, where it comes from, and what the Almanac thinks of the whole thing.

What Moon Phase Compatibility Actually Means

The premise is simple. Every person was born on a day when the Moon was in one of eight phases. The trend pairs two birth phases against each other. If the two illuminated portions, sketched side by side, complete a full circle, the test says the pair is compatible. If they overlap or leave a gap, the test says they are not. Think of it as a visual puzzle-piece game with the Moon as the pieces.

For example, a partner born under a waxing crescent and a partner born under a waning gibbous would, drawn together, form a roughly complete disk. By the trend’s rules, that pair is a match. Two new moons would not match because two zero-illumination phases cannot complete each other. Neither would two full moons, since there is nothing left to add.

Where the Trend Came From

The compatibility test traces to TikTok creator @lexihernandezz in January 2022. The video was steady but quiet for a year, then surged in March 2023 when a wave of duets and stitches turned it into a meme. The hashtag #moonphasecompatibility has logged more than 430 million views, with over 16 million pieces of content using the underlying filter. Mainstream coverage from Today, NBC News, ABC, and Yahoo all framed the trend as cultural entertainment rather than serious astrology, which is the right frame.

The Eight Phases Used

The test uses the standard astronomical lunar phases:

1. New moon. Moon is between Earth and Sun. Zero percent illuminated. A blank dark disk in the test.

2. Waxing crescent. Up to 49 percent illuminated, lit on the right (Northern Hemisphere). Looks like a D being drawn in.

3. First quarter. Right half lit. A clean half-moon.

4. Waxing gibbous. 51 to 99 percent lit, still growing.

5. Full moon. 100 percent illuminated.

6. Waning gibbous. 99 to 51 percent, shrinking.

7. Last quarter. Left half lit.

8. Waning crescent. 49 percent down to 0, lit on the left, looks like a fading C.

For a longer breakdown of how the cycle works, see our piece on the crescent moon. For the side of the Moon nobody on Earth ever sees, see the far side of the moon. For the side of the Moon nobody on Earth ever sees, see the far side of the moon.

How to Look Up Your Birth Moon Phase

You only need a date. The test does not require birth time, location, or any astrological chart. The calculation is straightforward astronomy.

Free calculators that give you the phase:

1. StarDate Moon Phase tool from McDonald Observatory at the University of Texas. Enter the year and month. NASA-affiliated and accurate.

2. timeanddate.com moon phase archive. Search any date back to 1900.

3. Farmers’ Almanac moon phases calendar. Lists every full moon, new moon, and quarter for the current year.

Once you have a date and an illumination percentage, drop the illumination into one of the eight phase buckets above. That is your birth phase.

Moon Phase Compatibility Is Not Astrology

This is the part most articles get wrong. Astrology and moon phase compatibility are different systems.

Astrological moon sign. Requires your exact date, exact birth time, and exact birth location. Refers to which zodiac sign the Moon occupied at the moment of birth (Aries through Pisces, twelve options). Used by astrologers to talk about emotional temperament.

Moon phase compatibility. Requires only your date. Refers to the Moon’s illumination percentage on that day (eight options). Has nothing to do with the zodiac.

If you have ever heard “I’m a Pisces moon,” that is the astrological moon sign system, not phase compatibility. Two different things, often confused.

The Almanac Take: Honest, Not Snobby

Farmers’ Almanac has used the Moon as a planning calendar since 1818. Plant aboveground crops on a waxing moon, plant root crops on a waning moon, fish on the right phase, that kind of guidance. We treat the Moon as a calendar, not as a fortune-teller.

So here is the honest read on moon phase compatibility. There is no peer-reviewed evidence that the phase the Moon was in on the day you were born has any effect on your personality, your relationships, or who you are compatible with. None. The test is a fun visual game, not a scientific or even a traditional astrological tool. The pairing rules were invented for TikTok in 2022. There is no folkloric tradition behind it.

That said, the puzzle-piece visual is genuinely charming, the underlying lunar mechanics are real and worth knowing, and there is nothing wrong with looking up two birthdays for fun and seeing whether the disks complete each other. Just go in with the right frame. It is entertainment, not insight.

If you want a use of the Moon that has 200 years of tradition behind it, see the Best Days Calendar. That one tells you when to plant tomatoes.

Quick How-To: Run the Test

Step 1. Get both birthdays.

Step 2. Look up each one’s moon phase using the calculators linked above.

Step 3. Sketch the two phases side by side, lit edges facing each other.

Step 4. Check the fit. Together, do they complete a full disk? The trend says yes equals compatible. Gaps or overlaps say no.

Step 5. Take it as the social game it is. Have fun. Read your actual partner.

Frequently Asked Questions

What is moon phase compatibility?

Moon phase compatibility is a TikTok trend that compares the lunar phase from each person’s birth date and checks whether the two phases, drawn side by side, complete a full moon. The hashtag has logged over 430 million views since 2023.

How do I find my moon phase?

Enter your birthday into a free moon-phase calculator like StarDate, timeanddate.com, or the Farmers’ Almanac moon phases calendar. You only need the date, not the time or location. The calculator returns the phase and illumination percentage for that day.

Is moon phase compatibility the same as astrology?

No. Astrological moon signs use the zodiac and require exact birth time and location. Moon phase compatibility uses only the date and refers to the Moon’s illumination percentage. They are different systems, often confused.

Is there scientific evidence behind moon phase compatibility?

No. There are no peer-reviewed studies showing that the lunar phase on a person’s birth date affects personality or relationship compatibility. The test is a viral entertainment trend, not a scientific or traditional astrological tool.

Where did the moon phase compatibility test come from?

TikTok creator @lexihernandezz posted the original test in January 2022. It went viral in March 2023 through duets and stitches, and the hashtag has since crossed 430 million views.

What are the eight moon phases the test uses?

New moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. The cycle takes about 29.5 days from one new moon to the next.