Free Quindecile Calculator

A quindecile is a 165° aspect between two planets, formed when they sit one-fifteenth of a circle off opposition. American astrologer Noel Tyl popularized it in the 1990s as the signature of obsession, compulsion, and unrelenting motivation, the chart's cause célèbre that refuses to let go. It belongs to the 24th harmonic and is classed as a minor aspect by orb but a major one by felt intensity.

That last part is where most explainers undersell it. The quindecile reads with the heat of a square. Not the friction of a quincunx, not the buzz of a quintile. When you find one in a chart, the person almost always knows what it points to. The aspect names a fixation they have already lived with.

If you can find an opposition, you can find a quindecile. Subtract 15° from 180° and you get 165°. Any two planets sitting that far apart, give or take 2°, are in quindecile.

The math is clean:

• A full circle is 360°.
• The 24th harmonic divides the circle into 15° slices.
• 11 of those slices makes 165°.
• 12 makes 180° (the opposition).

That single-slice difference is why the aspect feels so close to an opposition without ever resolving like one. An opposition wants integration. The quindecile wants release, and it never gets it, so it keeps applying pressure.

Do not confuse it with the quincunx. The quincunx (also called the inconjunct) sits at 150°, two slices off opposition. The quindecile is one slice off. If you see Venus at 5° Aries and Pluto at 5° Virgo, that is an exact quincunx (150°). Slide Pluto to 20° Virgo and the separation widens to 165°, a quindecile. Same two signs, fifteen extra degrees, completely different aspect family. The visual signature of the quindecile is “almost opposite but offset by one sign,” which is what makes it so easy to miss on the wheel.

Our default is 2°, matching the standard Noel Tyl set in his original research. That is the orb most working astrologers still use, and it is where the signal density is best. Pairs inside 1° hit hardest, 1° to 2° still earn interpretation, and pairs outside 2° tend to read as background noise rather than active obsession.

The orb is so much tighter than what you would use for a square or trine because of how the 24th harmonic decays. Every zodiacal degree counts for fifteen harmonic degrees at this level. A 2° orb in standard chart terms is already a 30° spread in the harmonic itself. Open it to 3° and you have widened a major aspect to 45°, which is meaningless. The signal washes out.

For reference, here is the range working astrologers use:

The orb switcher above lets you toggle between 1° tight, 2° standard, and 2.5° loose without recomputing the chart.

Ricki Reeves' framing is the cleanest way to think about quindeciles across chart types. Four modes, four temperatures.

Natal quindeciles: “The Fatal in the Natal.” Point to the obsessions a person was born with. Not goals they chose, fixations they inherited. Look first at the slower of the two planets and the house it sits in; that is the territory the obsession plays out on. Then look at the faster planet for the style: how it surfaces, what it sounds like in the chart holder's voice.

Progressed quindeciles: “The Obsession in Progression.” Secondary progressions and solar arc directions activate quindeciles slowly, often across a year or more of approach. These are the years where someone changes career around a single idea, or where a relationship pattern they have repeated for two decades finally surfaces into therapy.

Transit quindeciles: “The Bandit in the Transit.” Tyl called the transiting quindecile the bandit because it shows up uninvited and demands attention. A transiting outer planet in quindecile to a natal point lasts long enough to reshape a piece of the chart holder's life. Saturn quindecile to a natal Sun is a year of obligation that will not release. Pluto quindecile to a natal Moon is the slow internal renovation of an emotional pattern.

Synastry quindeciles: “The Need to Be.” Quindeciles between two charts read as compulsive attachment. The need to be near each other, with each other, working on each other. Reeves names this mode well: the relationship feels less like a choice and more like a magnetic correction the body is making against its own better judgement.

The interpretive shorthand below is a working scan, not a substitute for the calculator's pair-by-pair output. The calculator above writes a curated read for each pair it detects; this section gives you the underlying logic.

Read the slower of the two planets for the territory of obsession (where it plays out, which house, which life area). Read the faster planet for the style (how it surfaces, what it sounds like when the chart holder talks about it). A Sun-Pluto quindecile and a Moon-Pluto quindecile both have Pluto as the slow body, but they describe two different fixations: one about power and visibility, one about emotional fusion and control.

The diagonals worth circling are Sun-Pluto, Moon-Pluto, Venus-Pluto, Mars-Saturn, and Mercury-Neptune. These are the pairs that show up most often in the charts of people you would describe as driven past reason. Not because Pluto is special, more because the slower the outer planet, the harder the inner planet has to push against it.

Most quindecile writing stops at planet-to-planet pairs. That is a miss. Quindeciles to the Ascendant and Midheaven carry the same heat and arguably more directional information, because the angles anchor the chart in identity, vocation, and relationship.

Quindecile to the Ascendant or Descendant reads as obsession around identity-and-other, the version of yourself you present versus the version that comes out in close relationships. If you have a quindecile to your Ascendant or Descendant axis, the planet on the far end names the trait you cannot stop performing or the partner type you cannot stop attracting.

Quindecile to the Midheaven reads as career or public-role obsession. People with this often have a single visible identity that has eaten their interior life. The aspect needs handling, not curing.

The calculator above flags angle quindeciles with an Angle chip on the row so you can find them at a glance.

A quindecile in isolation is one thing. A quindecile that sits inside a larger configuration is another, and the configuration usually wins. Watch for these combinations:

• Yod with a quindecile foot. A standard Yod is two planets in sextile, both quincunx a third. Replace one of the quincunxes with a quindecile and the pressure on the apex planet sharpens. The chart holder does not just feel pulled toward the apex, they feel hunted by it.
• Thor's Hammer with a quindecile leg. A Thor's Hammer is two squares converging on a third planet via a sesquiquadrate. Add a quindecile from one of the legs to a fourth point and you get a configuration that will not release until the chart holder takes action of a specific shape.
• Stellium with an embedded quindecile. A stellium plus a single quindecile out to one outer planet reads as an entire life theme bent around one fixation.

The Aspect Pattern Scanner detects all of these and shows you where the quindecile sits inside the larger figure.

The quindecile has a longer credit list than most articles acknowledge.

The earliest serious treatment is Edward L. Johndro in the 1920s and Charles Jayne in the mid-twentieth century, both of whom worked through the 24th harmonic as part of broader minor-aspect research. Their writing is technical and largely out of print, but it is where the math first got worked out for a Western audience. Johndro wrote about the 165° contact without giving it a name, which is why some modern sources still call it the “Johndro aspect.”

Noel Tyl is the one who made the quindecile a fixture of modern practice. In the 1990s he ran extensive empirical research on the aspect, most famously through Leonardo da Vinci's chart, and standardized the 2° orb. His framing of the quindecile as the signature of obsession is the version almost every contemporary astrologer is downstream of, whether they cite him or not.

Ricki Reeves wrote the only book-length treatment of the aspect: The Quindecile: The Astrology & Psychology of Obsession (Llewellyn, 2003). Her four-mode framing (Fatal in the Natal, Obsession in Progression, Bandit in the Transit, Need to Be in Synastry) is the structural backbone most modern interpreters still use, including the one you are reading.

Bil Tierney's Dynamics of Aspect Analysis covers the quindecile inside the broader minor-aspect family rather than as a standalone subject, but his treatment of harmonic decay (why a 2° orb at the 24th harmonic is functionally wide) is still the cleanest theoretical justification for the tight orb.

If you want the original research, Tyl is where to start. If you want the working interpretation, Reeves. If you want the math, Tierney and Jayne.

A quick orientation in the minor-aspect family, because the quindecile gets confused with all of these and deserves not to be:

• Quincunx (150°): the inconjunct, two signs apart in a way that will not blend. Reads as friction, mismatch, sometimes health. Not obsession.
• Semi-sextile (30°): minor twelfth-harmonic, mild support or mild irritation depending on the planets. Our Semi-Sextile Calculator walks through every case.
• Sesquiquadrate (135°): friction with a delayed release. The slow-burn version of a square.
• Quintile (72°) and biquintile (144°): the fifth-harmonic family, which reads as creative gift or singular talent. A different family entirely.
• Septile (51.4°) and novile (40°): the seventh and ninth harmonic aspects, carrying fated or spiritual color depending on which tradition you read.

The quindecile is the only standard minor aspect that reads with the heat of a major. That is why it earned its own book, and it is why most software treats it as a special case rather than lumping it with the rest of the minor family.