Transit chart calculator: your transits today

Your birth chart is a snapshot: where the Sun, Moon and planets stood at the minute you were born, seen from your birthplace. It never changes. The sky does, and a transit chart puts the two side by side. On the wheel above, your natal planets sit on the inner ring and today's planets on the outer ring, both on the same zodiac band.

A transit happens when a moving planet forms an aspect to one of your natal points. The five classic aspects are angles: the conjunction (0 degrees apart), the sextile (60), the square (90), the trine (120) and the opposition (180). An aspect counts while the planets are within a few degrees of that angle, a margin called the orb. This calculator uses 4 degrees, so the list holds the contacts that are close right now.

How long a transit lasts depends on how fast the moving planet travels. The Moon covers about 13 degrees a day, so a lunar transit comes and goes within a day. The Sun moves about one degree a day and stays within 4 degrees of an aspect for roughly eight days. Mercury, Venus and Mars take days to a few weeks, depending on their speed and on whether they are slowing down to turn retrograde.

The slow planets are different. Jupiter can stay in orb for months, and Saturn, Uranus, Neptune and Pluto for most of a year or longer, because their retrograde loops can carry them back across the same degree up to three times. That is why astrologers give the slow transits the most weight: they mark the longer chapters, while the fast ones color single days. The list puts them first for the same reason.

Every transit in the list is marked as building or easing. Building (astrologers say applying) means the moving planet is still closing in on the exact angle; easing (separating) means the exact moment has passed and the orb is widening. The calculator reads this from the sky ten minutes later, so it is right even for the Moon.

Tradition reads a building transit as a theme that is still gathering and an easing one as a theme being absorbed. When a slow planet turns retrograde, a transit that was easing can start building again, which is how the same contact returns weeks or months later.

Start at the top of the list. The strongest transits involve a slow planet, one of your personal points (your Sun, Moon, Ascendant or Midheaven) and a tight orb, and the ranking weighs all three, along with the aspect itself. Then look at the aspect: astrologers read trines and sextiles as easy, flowing contacts, squares and oppositions as friction that asks for effort, and the conjunction as an intensifier that takes on the character of the planet involved.

The houses add the where. The table of today's planets shows which of your houses each planet is crossing today; the transits guide explains what each house stands for. For a walk-through of one transit from start to finish, read how a transit touches your chart.

Your birth date, time and place are turned into Universal Time with the historical time zone rules of that place. Our engine then computes the apparent positions of the Sun, Moon and planets for your birth and for this minute: VSOP87 for the Sun and the planets from Mercury to Neptune, Meeus's series for Pluto and the ELP2000-82 lunar theory for the Moon, corrected for light time, aberration and nutation, in the tropical zodiac. We test the engine against NASA JPL's Horizons ephemeris; the accuracy page shows the comparison.

Everything is calculated in your browser. For today's first line, your birth details are sent once to our server and not stored; only the place search sends the name you type to Photon, the OpenStreetMap geocoder. The calculator is free and needs no account.