Moon phase compatibility calculator

How to do the moon phase soulmate test

1. Switch to Moon Match. Use the toggle above the form, or the direct soulmate test link.
2. Enter two birth dates. Yours and the other person's — the date alone is enough, no birth time needed.
3. Read the result. You'll see both birth moons side by side, a 0–100 compatibility score, and which of the four match bands you land in.

Everything runs in your browser — the dates are never uploaded anywhere.

What your compatibility score means

The score measures how close your two birth phases sit on the lunar cycle: a score of 100 means the same phase, 0 means exact opposites. Four bands cover the range:

• Mirror Moons (85–100) — born under nearly the same phase, about 2 days apart at most. Familiar rhythms; you recognize your own energy in each other.
• Heart Match (65–84) — neighboring phases roughly 2–5 days apart. This is where the pairing behind the trend's heart image lands: a waxing and a waning crescent whose lit edges face each other.
• Balance Match (45–64) — a moderate gap of roughly 5–8 days that mixes similarity with contrast. Enough common ground to feel at ease, enough difference to stay interesting.
• Contrast Match (0–44) — opposite sides of the cycle, more than about 8 days apart. The two-halves reading of the trend: one of you bright where the other is dark.

Under the hood, the calculator measures the shorter arc between your two phases on the 0–1 lunar cycle — a distance from 0 to 0.5 — and converts it with score = 100 × (1 − distance ÷ 0.5). A same-phase pair scores 100; a new moon paired with a full moon scores 0.

How moon phases are calculated

The moon phase is calculated astronomically using the SunCalc library, which models the synodic lunar cycle — the time from one new moon to the next — at approximately 29.53 days. For any given date, SunCalc computes the moon's illumination fraction and its position within the cycle (expressed as a 0–1 value from new moon back to new moon), placing it in one of eight named phases: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent. All calculations happen entirely in your browser. Learn more on our methodology page.

Where the soulmate test comes from

The moon phase soulmate test went viral on TikTok in 2023, driven by CapCut templates that set screenshots of two birth moons side by side so the crescents form a heart. Morning shows and almanac sites picked it up, and couples have been comparing birth moons ever since.

This calculator replaces the screenshots with the underlying astronomy: it computes each phase from the birth date directly, scores the pairing on a transparent 0–100 scale, and gives the same answer every time — no video template required.

Frequently asked questions

What's a moon phase soulmate?

The "moon phase soulmate" idea comes from social media, where you compare the lunar phases on two people's birthdays. The trend has two popular readings: crescents from neighboring phases that visually form a heart when placed side by side, and opposite phases — one new moon, one full moon — said to complete each other like two halves of a whole. This calculator computes the actual astronomical phase for each birth date and converts the distance between them into a 0–100 score, so you can see where your pairing lands — and which of those two readings it comes closer to.

Why did my result say Heart Match?

Heart Match is the 65–84 score band. It appears when your two birth phases sit close together without being identical — roughly 2 to 5 days apart on the 29.53-day lunar cycle. The heart image from the trend, a waxing crescent and a waning crescent laid side by side with their lit edges facing each other, is exactly this kind of pairing: two neighboring phases on either side of the new moon.

Is this scientific?

The moon phase calculation is astronomically accurate — it uses the SunCalc library, which models the synodic lunar cycle (≈29.53 days) using standard celestial mechanics. The calculated phase for any date will match published almanac data. The compatibility interpretation, however, is a numerological and cultural tradition, not a scientific claim. We present it as a tool for self-reflection and entertainment, not as a prediction about your relationships.

Which moon phases make the best couple?

No pairing wins outright — the four bands describe different dynamics rather than a ranking. Mirror Moons (85–100) means you were born under nearly the same moon. Heart Match (65–84) pairs neighboring phases. Balance Match (45–64) mixes similarity with contrast. Contrast Match (0–44) joins opposite sides of the cycle, which the trend itself often celebrates as two halves of one moon. Like the other readings on this site, these are traditions for self-reflection, not predictions.

What does a low score mean?

A score under 45 means your birth phases sit more than about 8 days apart on the lunar cycle, and a score of 0 means exact opposites, such as one new moon and one full moon. It is not a verdict on the relationship. In the original trend, opposite phases are often read as completing each other — the two-halves-of-a-whole pairing — so a low score signals difference and spark rather than incompatibility.