Part of Fortune Calculator and the Seven Lots

Your Part of Fortune is the point you reach by measuring the distance from the Sun to the Moon in your chart and counting the same distance on from your Ascendant. It is the best known of the lots, also called parts or Arabic parts. The tool works out Fortune and the six other lots the Hellenistic tradition credits to Hermes, tells you whether yours is a day or a night chart, and shows each formula with your own positions. It needs your birth time.

How it works

Day or night. A chart is a day chart when the Sun is above the horizon at birth, in the half of the chart from the Descendant round to the Ascendant, and a night chart when it is below. The tool checks this from your birth time and place. If a birth a few minutes earlier or later would change it, the result says by how many minutes.

The Part of Fortune. Ptolemy gives it in the Tetrabiblos, book III, chapter 10 (Of Length of Life): take the distance from the Sun to the Moon and count it on from the Ascendant, in the order of the signs, by day and by night alike. Most Hellenistic astrologers turned the measurement round at night, from the Moon to the Sun, and the tool follows them; for a night chart it also shows where Ptolemy’s rule would put your Fortune.

The seven lots. These are the lots the Hellenistic tradition credits to Hermes, as Paulus Alexandrinus (4th century CE) gives them in his Introductory Matters. Each is the Ascendant plus one position minus another, and at night each formula is turned round:

The ruler of each lot’s sign uses the traditional rulers in the Tetrabiblos, book I, chapter 17. Your planets are tropical positions from NASA JPL DE440 data, and the Ascendant and houses come from your birth time and place, with the time zone and daylight saving in force there on that date.

Reading the result

The result gives each lot’s sign and degree, its house, the planet that rules its sign, and the formula with your positions. Each lot is paired with the planet in its formula: Fortune with the Moon, Spirit with the Sun, Eros with Venus, Necessity with Mercury, Courage with Mars, Victory with Jupiter and Nemesis with Saturn. Fortune is read for the body and what comes to you, Spirit for the mind and what you choose to do, and the others by their names. Readers look at the house a lot falls in, and at the planet that rules its sign, as the place in life where its theme plays out.

A birth close to sunrise or sunset can sit right on the line between a day and a night chart. If yours is within half an hour of that line, the tool says by how many minutes: read both versions if your birth time is not exact.

Where traditions differ

Ptolemy kept one formula for Fortune by day and by night; most other ancient authors reversed it at night. Some writers, among them Vettius Valens, give other formulas for some lots, notably Eros and Necessity; this tool follows the Hermetic list as Paulus gives it. The name Arabic parts comes from the medieval astrologers writing in Arabic, such as Abu Ma’shar, through whom the lots reached medieval astrology, where many more were added. You can show the houses in the Placidus or the Whole Sign system.

What it does not do

It cannot work without a birth time, because the Ascendant changes sign about every two hours. It does not list the many later medieval parts, and it does not forecast events: the lots describe themes in a chart, and none of them is a warning or a promise.

Frequently asked questions