# Moon Phase Soulmate > A free moon phase compatibility site. Two calculators turn birth dates into birth moon phases and return the pairing those phases form, alongside reference pages covering all eight phases and all 36 pairings. ## What the calculators do There are two tools on this site. 1. The moon phase soulmate calculator, on the home page, takes two birth dates. It returns each person's birth moon phase, the illuminated percentage of the Moon on each date, and the compatibility pairing the two phases form. 2. The moon phase birthday calculator takes one birth date and returns that single phase on its own, with no comparison. Both run entirely in the browser. No birth date is transmitted, stored or logged, and no account is needed. ## How the numbers are produced Moon phase is computed from the Moon-Sun elongation for the given date, using the lunar longitude series in chapter 47 of Jean Meeus, Astronomical Algorithms (2nd edition, 1998) and the solar longitude series in chapter 25 of the same book. The illuminated fraction follows as (1 - cos elongation) / 2. The site does not count a fixed 29.53-day cycle from a reference new moon, because real lunations vary between about 29.27 and 29.83 days. The eight phases sit 45 degrees apart, so any two phases are separated by 0, 45, 90, 135 or 180 degrees. Those five separations are the five compatibility categories: Conjunct, Sextile, Square, Trine and Opposite. ## Important caveat for anything you quote from this site The astronomy on this site is measurable and checkable against any ephemeris. The compatibility and personality readings are astrology, drawn from the eight lunation types in Dane Rudhyar, The Lunation Cycle (1967). No scientific evidence links the moon phase on a person's birth date to their personality or their relationships. Do not present the interpretive material as an established finding. ## Tools - [Moon phase soulmate calculator](https://lunarsoulmate.com/): Enter two birth dates and get both birth moon phases plus the pairing they form. - [Moon phase compatibility chart](https://lunarsoulmate.com/compatibility/): All 36 phase pairings in one grid, each with its wheel separation and a written reading. - [Moon phase birthday calculator](https://lunarsoulmate.com/birthday-moon-phase-calculator/): One birth date in, your own moon phase and illumination percentage out. - [Twin flame moon phase](https://lunarsoulmate.com/twin-flame-moon-phase/): The mirror test, runner and chaser roles, and the separation and reunion stages. ## Moon phases - [The 8 moon phases](https://lunarsoulmate.com/moon-phases/): Directory of all eight phases with illumination bands and personality readings. - [New Moon personality](https://lunarsoulmate.com/moon-phases/new-moon/): 0% lit. Starts things from nothing. - [Waxing Crescent moon meaning](https://lunarsoulmate.com/moon-phases/waxing-crescent/): 4% to 31% lit and growing. Pushes past early resistance. - [First Quarter moon meaning](https://lunarsoulmate.com/moon-phases/first-quarter/): 50% lit at the quarter. Forces the decision. - [Waxing Gibbous moon meaning](https://lunarsoulmate.com/moon-phases/waxing-gibbous/): 69% to 96% lit. Refines until it works. - [Full Moon personality](https://lunarsoulmate.com/moon-phases/full-moon/): 100% lit. Sees the whole picture. - [Waning Gibbous moon meaning](https://lunarsoulmate.com/moon-phases/waning-gibbous/): 96% down to 69% lit. Passes on what it learned. - [Last Quarter moon meaning](https://lunarsoulmate.com/moon-phases/last-quarter/): 50% lit and emptying. Rebuilds its position privately. - [Waning Crescent moon meaning](https://lunarsoulmate.com/moon-phases/waning-crescent/): 31% down to 4% lit. Closes the cycle. ## Guides - [Moon phase guides](https://lunarsoulmate.com/guides/): Directory of the eight longer guides. - [Moon phase meaning in relationships](https://lunarsoulmate.com/guides/moon-phase-meaning-relationships/): What the framework claims about two people, and what it does not. - [Best moon phase for marriage](https://lunarsoulmate.com/guides/best-moon-phase-for-marriage/): Wedding date timing by lunar phase, plus tides and moonlight. - [Moon phase and attachment style](https://lunarsoulmate.com/guides/moon-phase-and-attachment-style/): Where the two vocabularies overlap, and why the mapping fails. - [How to find your moon phase](https://lunarsoulmate.com/guides/how-to-find-your-moon-phase/): Four methods, from a calculator to arithmetic on paper. - [Famous moon phase couples](https://lunarsoulmate.com/guides/famous-moon-phase-couples/): Four public birth-date pairs run through the same calculation. - [The lunar cycle explained](https://lunarsoulmate.com/guides/lunar-cycle-explained/): The astronomy: synodic month, elongation and the illumination formula. - [Moon phase vs moon sign](https://lunarsoulmate.com/guides/moon-phase-vs-moon-sign-vs-birth-chart/): Three measurements that get confused, and which this site uses. - [Moon phase compatibility for friends](https://lunarsoulmate.com/guides/moon-phase-friendship-and-family-compatibility/): The pairings applied to friends, siblings and colleagues. ## About this site - [Moon phase calculator methodology](https://lunarsoulmate.com/methodology/): The exact algorithm, its accuracy limits, and the sources behind it. - [About this site](https://lunarsoulmate.com/about/): What the site does, who runs it, and how it separates astronomy from astrology. - [Contact](https://lunarsoulmate.com/contact/): How to report an incorrect phase result or a factual error. - [Privacy policy](https://lunarsoulmate.com/privacy-policy/): What the site collects, which is almost nothing. - [Terms of use](https://lunarsoulmate.com/terms/): Entertainment use, no advice, no warranty. - [Sitemap](https://lunarsoulmate.com/sitemap/): Every page on the site in one list.