MBTI and Astrology
21 August 2026, by Lorris Turpin
This page does one simple thing: it computes your MBTI type (the sixteen personality types, like INFJ or ENFP) directly from your birth chart. Enter your birth date, time and place in the calculator further down, and your type appears twice: once by the classic tropical zodiac, once by the Aditya circle.
The core idea fits in one sentence: MBTI is built on Carl Jung's four psychological functions, and those four functions correspond to astrology's four elements.
- Fire = Intuition (N)
- Earth = Sensing (S)
- Air = Thinking (T)
- Water = Feeling (F)
The rest follows on its own: the Sun carries the outward-facing function, the Moon the inward-facing one, day or night birth says which of the two leads (E or I), and the kind of the Sun's element gives the last letter (J or P). Four letters, one type.
The full rule the calculator uses is right below, readable by everyone. The complete research article, for subscribers, shows where all of this comes from: Jung's definitions quoted at length, the function-to-element mapping argued against his texts, the alternative hypothesis, and the protocol for testing both.
The calculator's rule: the Sun outside, the Moon inside
(In the subscriber research article this rule goes by the name "Hypothesis 2": the attitude comes from the planet's gender.)
Let's take the four letters one by one, in the order the calculator writes them.
1. The Sun and the Moon share the work. The Sun is a masculine planet, the Moon a feminine one, whatever sign they sit in. So the Sun always carries the extraverted function, the one you show the world; the Moon always carries the introverted function, the one working within. The sign only supplies the element, and therefore the function. A Sun in a Water sign is Feeling shown to the world: exactly Jung's extraverted feeling. A Moon in a Fire sign is an intuition keeping watch inside: introverted intuition. Your two lights thus write two of the type's letters: the perceiving one (S or N) and the judging one (T or F).
2. Day or night decides who leads: E or I. In theory several rules compete for the answer: day or night birth, the Moon's visibility (a New Moon night is not a Full Moon night), strength by sign (dignity, Shadbala). For the calculator further down, one rule was chosen in advance, the simplest: day or night birth, measured against the exact Ascendant-Descendant axis. Sun above that axis = day birth = the Sun leads (E type); below = night birth = the Moon leads (I type). Boundary convention, worth knowing: the Sun sitting exactly on the Ascendant counts as night, and exactly on the Descendant as day. The other rules remain candidates to test; in the table below, the E/I column still reads as "whichever light leads".
3. The Sun's element gives the last letter: J or P. Myers' J/P letter names the kind of the extraverted function, and here that is always the Sun's: Sun in Air or Water (judging elements) = J, Sun in Fire or Earth (perceiving elements) = P. It holds for all 16 rows of the table below. To be exact about what that proves: this rule is internally isomorphic to Myers' type dynamics (it was built on the same two assumptions), so the J/P column is a consistency check, not evidence from charts.
4. And the count comes out exact. Every MBTI type has one extraverted and one introverted function, of different kinds. So every type is one ordered Sun/Moon element pair. There are 4 x 4 = 16 pairs; 8 of them are of different kinds, and each gives two types depending on which light leads: Sun dominant = E type, Moon dominant = I type. 8 x 2 = 16. The code closes, and the whole table fits on one page:
| Type | Sun (extraverted function) | Moon (introverted function) | Dominant light | Attitude | J/P from Sun |
|---|---|---|---|---|---|
| ISTJ | Air | Earth | Moon | I | J ✓ |
| ESTJ | Air | Earth | Sun | E | J ✓ |
| INTJ | Air | Fire | Moon | I | J ✓ |
| ENTJ | Air | Fire | Sun | E | J ✓ |
| ISTP | Earth | Air | Moon | I | P ✓ |
| ESTP | Earth | Air | Sun | E | P ✓ |
| ISFP | Earth | Water | Moon | I | P ✓ |
| ESFP | Earth | Water | Sun | E | P ✓ |
| INTP | Fire | Air | Moon | I | P ✓ |
| ENTP | Fire | Air | Sun | E | P ✓ |
| INFP | Fire | Water | Moon | I | P ✓ |
| ENFP | Fire | Water | Sun | E | P ✓ |
| ISFJ | Water | Earth | Moon | I | J ✓ |
| ESFJ | Water | Earth | Sun | E | J ✓ |
| INFJ | Water | Fire | Moon | I | J ✓ |
| ENFJ | Water | Fire | Sun | E | J ✓ |
The special case: when both lights say the same thing. Sun and Moon both in perceiving elements (Fire/Earth in any order) or both in judging elements (Air/Water), including same-element pairs, do not give one function of each kind: the two lights alone cannot write all four letters. H2 predicts those people test inconsistently, or flip letters between tests. That is a falsifiable prediction. The calculator further down still shows a complete type for these pairs: the missing letter is taken from the stronger of the two candidate elements in that frame's Elements pie, a deliberately simple, somewhat arbitrary choice, labeled as such under each result.
That is all the theory you need. Enter your birth below and see what your own chart answers.
Try it on your chart
The wheel below is the same one as the chart generator: same form, same celebrity library, and your saved charts work here too. Calculate a chart and two readings appear:
- The H2 deduction, one card per zodiac (Aditya circle and tropical western): day or night birth fixes which light leads, every letter of the type is explained line by line, and when neither the Sun nor the Moon supplies a letter, it is taken from that frame's Elements pie (a choice labeled as arbitrary).
- The elements-only reading: the whole element distribution votes on each axis, with leaning bars and percentages, the way an MBTI test reports its results. As in the pie, the Sun and Moon weigh 1.5 and Rahu, Ketu and the outer planets are excluded.
The two readings can disagree with each other and between the two zodiacs: that disagreement is part of what this page invites you to observe.
You have your type. The real question remains: where do these rules come from? Why would Fire be Intuition and Water be Feeling? What did Jung actually write, and which competing hypothesis was tried and set aside? That is what the rest of the article shows.