Free tool · tropical zodiac · ten bodies · checks degrees, not sign labels
T-square calculator
An opposition on its own isn’t a T-square. A T-square is three planets: two about 180° apart (an opposition), and a third about 90° from both of them (two squares). That third planet is usually called the apex. This calculator finds the apex and shows all three aspects with their actual degrees, so you can check them yourself. It needs a recorded birth time.
Check three pairs, not the shape of a drawing:
- The two base planets are about 180° apart (opposition).
- The first base planet is about 90° from the apex (square).
- The second base planet is also about 90° from the apex (square).
A T-square isn’t a diagnosis, a trauma marker or a fate verdict. It’s a geometric pattern between three planets, and the calculator reports only the degrees.
Example: a fictional chart
This is Lunara’s invented sample chart, not your chart or a real person’s: 1 January 1990, 12:00, London, the same fictional chart as the sample reading.
It has no T-square. Between its ten bodies it has 2 oppositions and one square, but no planet is square to both ends of an opposition, so none of them closes into the three-planet shape:
- Sun–Jupiter opposition, 5.67° from exact (allowed 7.50°)
- Jupiter–Uranus opposition, 0.64° from exact (allowed 5.50°)
- Moon–Mars square, 6.73° from exact (allowed 7.30°)
An opposition on its own, even a close one, isn’t a T-square.
Check your chart
Your birth details and chart are kept only in this page’s memory for this calculation, never in the page address or browser storage. If you open your full chart and buy a reading, the details needed to write it are stored with your order.
What counts as a T-square here
Three different planets where the calculation finds all three aspects: one opposition between the base planets and a square from each of them to the apex. The calculator checks degrees, not signs or modality. Planets in signs that look right can miss by a few degrees, and a planet near the edge of a sign can still count.
Lunara’s chart allows 6° either side of 180° for an opposition and 5.8° either side of 90° for a square. When the Sun or Moon is one of the pair, the allowance grows by 1.5° (once, even for the Sun and Moon together). When Uranus, Neptune or Pluto is one of the pair, it shrinks by 0.5° (also once). A pair with a luminary and one of those outer planets gets both adjustments. The table shows the allowance used for each pair, and a pair close to its allowance is the part most likely to differ on another site.
These are this site’s settings, not a universal rule. Another calculator may use stricter or wider orbs, or add the nodes, Chiron or the angles, so its answer can differ from this one. A T-square can also be three corners of a four-planet grand cross; this tool doesn’t check for that fourth planet either way, but the grand cross calculator does.
A prompt, with or without one
Astrologers often read a T-square as two things pulling in opposite directions, with a third place where the pressure gets worked out. You can use that idea as a reflection whether or not your chart has one. An invented example: “Saving money and seeing friends keep pulling against each other; the place I can act is how I plan weekends.”
The two priorities pulling against each other: ___
One small action I’ll choose this week that serves both: ___
Write it wherever you like; this page doesn’t ask for or keep your answers. It’s a reflection, not a reading of your chart or a promise of any result.
Read more: grand trine calculator · Yod calculator · major aspects calculator · how to read a birth chart.
Frequently asked questions
- What is the apex of a T-square?
- The apex is the planet that is about 90° from both planets of an opposition. In the result, the apex is listed first, the opposition row comes next, and each square row names the apex.
- Are three planets in cardinal, fixed or mutable signs a T-square?
- Not necessarily. Signs of the same modality are 90° or 180° apart as signs, but the planets’ degrees decide. A planet at 1° Aries and another at 29° Cancer are almost 118° apart, nowhere near a square. A pattern can also cross modalities when a planet sits near the edge of a sign.
- Is it part of a grand cross?
- Possibly. A grand cross is four planets: two oppositions and four squares. Any three of them also meet the T-square definition. This calculator doesn’t check for a fourth planet, so it doesn’t say whether your T-square is part of a grand cross, and it doesn’t say the opposite point is empty either.
- Why does another site show a different result?
- Calculators use different orbs, and some include extra points such as the nodes, Chiron or the Ascendant. A square near the edge of its orb can count on one site and not on another. This page uses Lunara’s settings, listed above, and only the ten bodies.
- What does it mean if I don’t have one?
- Only that no three of your ten bodies meet all three conditions within these orbs. It doesn’t mean anything is missing from your chart, and the prompt on this page works without a T-square.
- Why does it need a recorded birth time?
- The Moon moves about 12° to 15° a day, so whether it makes a square or opposition can change between morning and evening. Slower planets usually keep the same aspects all day, but this page doesn’t guess: it won’t fill in midnight or noon. The full chart’s houses also depend on the exact time. Without a recorded time, see the guide to a birth chart without a birth time.
Method: Lunara’s central Swiss Ephemeris calculation, tropical zodiac, geocentric. T-squares come from the same pattern detection as the free birth chart, limited here to Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto; nodes, Chiron and the chart angles are left out. Each of the three aspects comes from the same aspect calculation, with the orb weighting described above. Each group is listed once, by its apex and its opposing pair. Text written with AI assistance. A T-square is a symbolic pattern in astrology, not a prediction, diagnosis or measure of how your life will go.