Arabic parts calculator
A lot is a point measured out from the Ascendant using the distance between two other places in the chart. Nothing is orbiting there; the position is arithmetic on three numbers you already have.
Your birth details
The name is an accident of transmission. These points reached Europe through Arabic sources and picked up the label Arabic parts along the way, but the technique is older than that and Hellenistic astrologers were already using it. The Greek word is kleros, a lot in the sense of an allotment.
Most lots reverse their formula between a day birth and a night birth, and this is not a decoration. The Part of Fortune is Ascendant plus Moon minus Sun by day and Ascendant plus Sun minus Moon by night, which mirrors the point across the Ascendant rather than nudging it. This calculator shows which form your chart used, so that the number can be compared with anyone else's.
What a lot gives you is a place in the chart, not a verdict. Read the sign and the house it falls in, and look at the planet ruling that sign, which is where the tradition says the matter is actually handled. Nothing here forecasts an event.
Your seven Hermetic lots
Part of Fortune
The lot of the Moon and the most used of the seven: the body, the circumstances you are given, and what the tradition calls fortune in the sense of what arrives rather than what is chosen.
Read about this lotPart of Spirit
The lot of the Sun and the mirror of Fortune: deliberate action, the part of a life that is willed rather than received.
Read about this lotLot of Eros
The lot of Venus: desire and what one is drawn toward, read in the classical sources as appetite rather than romance alone.
Read about this lotLot of Necessity
The lot of Mercury: constraint, the things that cannot be argued with, and in the older material litigation and enmity.
Read about this lotLot of Courage
The lot of Mars: boldness and the capacity to act under pressure, built from Fortune rather than from Spirit.
Read about this lotLot of Victory
The lot of Jupiter: confidence, trust and what one succeeds at, the most straightforwardly benefic of the seven.
Read about this lotLot of Nemesis
The lot of Saturn: limit and what is hidden or delayed, named for the goddess of retribution but read as the place where the account comes due.
Read about this lotThe engine calculates fourteen lots. This page shows the seven Hermetic lots described by Paulus Alexandrinus, one for each classical planet, because that is a set with a source rather than a selection we made up. The remaining seven are medieval and later additions covering marriage, children, commerce, inheritance and death, and they do not belong to this set.
Frequently asked questions
What are the Arabic parts?
They are points calculated from three positions in the chart, almost always the Ascendant plus one body minus another. The name comes from their transmission through Arabic sources, but the technique is Hellenistic and the Greek term is kleros, meaning a lot or allotment. They are derived points rather than bodies.
Why does the formula change for a night birth?
Because most lots are built from a sect-dependent pair, and reversing the two terms mirrors the point across the Ascendant. The Part of Fortune is Ascendant plus Moon minus Sun by day and Ascendant plus Sun minus Moon by night. The two results are equidistant from the Ascendant on opposite sides, so using the wrong one does not shift the lot slightly, it puts it somewhere else entirely.
Do I need an exact birth time?
Yes. Every lot is measured from the Ascendant, which moves roughly a degree every four minutes, and the day or night distinction depends on whether the Sun is above the horizon. An approximate time can change both the position and the formula, so this calculator asks for a real one rather than defaulting to noon.
How many Arabic parts are there?
There is no fixed number. Medieval sources list dozens, and later authors kept adding. The seven shown here are the Hermetic lots of Paulus Alexandrinus, one per classical planet, which is the oldest coherent set. Treating every lot ever proposed as equally weighted is one of the ways this technique gets diluted.