Hellenistic · Arabic Tradition · Lot Calculation

Arabic Parts Calculator

Twelve classical lots — the Hermetic core plus key Bonatti–Lilly era points, with diurnal/nocturnal formulae at degree precision.

What Is a Lot (κλήρος · sahm · pars)?

Lots — Greek klēros "allotment, share", Arabic sahm "arrow, share", Latin pars "part" — are derived points in a natal chart that measure the ecliptic distance between two planets (or luminaries) projected onto a reference point, usually the Ascendant. A lot is not a "planet"; it is a symbolic distance, a configuration.

The general formula is: Ascendant + A − B. That is: the arc from planet B to planet A is cast forward from the Ascendant. The reversal of formula for day/night birth sits at the heart of Hellenistic doctrine: because the roles of the luminaries change according to sect, a lot also flips its polarity depending on which light leads the chart.

These points pass from the Hellenistic tradition (Valens, Paulus, Dorotheus, the lost works ascribed to Hermes) through the Islamic golden age (Māshā'allāh, Sahl ibn Bishr, Abū Maʿshar, al-Bīrūnī) where they were expanded, and then through Latin translations (Bonatti, Lilly) into Europe. The name "Arabic parts" reflects this transmission line; most of the lots themselves are Greek in origin.

Enter Planet Degrees (Ecliptic 0–359.99°)

Enter each planet's ecliptic longitude in the 0–359.99 range (0° = Aries 0°, 30° = Taurus 0°, 120° = Leo 0°, etc.). If in doubt, copy the "ecliptic longitude" value from your astrology software.

e.g. 105.50 → Cancer 15°30'
Scorpio 7°12'
Taurus 28°24'
12 cusps in degrees, comma-separated. Leave blank to show signs only.
Sect (Birth) · Diurnal or Nocturnal?

Primary and Secondary Sources

  • Vettius Valens, Anthologies Books II–V (2nd c. CE) — applied doctrine of the klēroi, the lots of Fortune and Daimon.
  • Paulus Alexandrinus, Eisagogika §23 (4th c. CE) — sequential presentation of the seven Hermetic lots.
  • Dorotheus of Sidon, Carmen Astrologicum Books I & III (1st c. CE) — marriage, children, travel lots.
  • Panaretos ascribed to Hermes Trismegistus (lost, preserved through Paulus) — the attributed source of the Hermetic core.
  • Māshā'allāh, Kitāb al-Mawālīd (8th c. CE) — expansion of lots in the Arabic tradition.
  • Abū Maʿshar (Albumasar), Mudhākarāt & Kitāb al-Madkhal — the doctrine of sahm in classical Arabic systematics.
  • al-Bīrūnī, Kitāb al-Tafhīm §475 ff. (1029 CE) — a list of 97 sahms with formulae.
  • Guido Bonatti, Liber Astronomiae Tract V (13th c. CE) — Latin partes, house-themed lots.
  • William Lilly, Christian Astrology Vols II–III (1647) — pars in horary and natal practice.
  • Brennan, Chris. Hellenistic Astrology: The Study of Fate and Fortune, Amor Fati, 2017 — lots chapter.
  • Schmidt, Robert. Project Hindsight translations (Valens, Paulus, Dorotheus) — English editions of the primary texts.

Keep this tool's academic report at hand

The 12 lots' computed values + classical formula card as a PDF. Join our email list.

Frequently Asked Questions

About the classical Arabic Parts (lots / partes)

What are Arabic Parts (Lots)?

Lots (Greek klēros, Arabic sahm, Latin pars) are derived points in a natal chart that measure the ecliptic distance between two planets or luminaries projected onto a reference point (typically the Ascendant). They are not planets; they are symbolic configurations. The most famous is the Lot of Fortune (Pars Fortunae): it represents bodily life, health and material affairs.

How is the Lot of Fortune calculated?

For a diurnal (day) birth: ASC + Moon − Sun. For a nocturnal (night) birth the formula reverses: ASC + Sun − Moon. All arithmetic is done modulo 360 (add 360 if the result is negative, subtract 360 if it exceeds 360). Example: ASC 105°, Moon 60°, Sun 220° in a day chart → 105 + 60 − 220 = −55 → +360 = 305° = Capricorn 5°.

Why do lots reverse for day and night births?

Because in Hellenistic doctrine the roles of Sun and Moon change with sect (hairesis). In a day chart the Sun is the "sect leader" (the primary light); the Moon plays a supporting role. In a night chart the situation reverses. The lot formulae mirror this role swap of the lights: bodily life (Fortune) in the day chart is projected from the Moon (the secondary light) to the Sun; at night it is the reverse. Valens makes this explicit; in modern astrology the loss of this rule is the single most common source of wrong lot calculations.

What is the difference between Hellenistic and Bonatti lots?

The Hermetic seven lots (Fortune, Spirit, Eros, Necessity, Courage, Victory, Nemesis) from the Hellenistic period fully reverse the formula for day and night. Bonatti, Lilly and the Latin medieval tradition in general do not apply sect reversal to most lots; a single formula is used. This is not an oversight but a historical preference — the Latin tradition emphasised pragmatic natal application. Modern classicists usually prefer the Hellenistic (reversing) formulation.

Are the Hermetic 7 Lots different from the other lots?

Yes. The Hermetic seven lots (Fortune, Spirit, Eros, Necessity, Courage, Victory, Nemesis) come from a lost text called Panaretos ("all-virtuous") attributed to Hermes Trismegistus and transmitted by Paulus Alexandrinus in his famous §23. They are the classical core: they weave the full matrix of light–planet relationships. Other lots (marriage, children, travel, trade, inheritance, etc.) are medieval developments, derived by the Arabic tradition and Bonatti to address specific natal themes. Şira Nur Uysal's Hermetic Lots Calculator focuses on this seven-fold core; the present tool offers the wider classical repertoire.

Why are lots little-known in modern astrology?

Lots were central throughout the Hellenistic–Arabic–Latin chain; al-Bīrūnī catalogues 97 of them. With the late 19th-century rise of psychological/modern astrology they were dismissed as "symbolic overload" and dropped. Even Pars Fortunae, while still plotted in most modern charts, was rarely interpreted. The Project Hindsight translations of Robert Schmidt and Robert Hand in the 1990s, followed by Chris Brennan's 2017 study, returned lots to the academic–practical standard. Today every astrologer working with classical techniques knows at least the seven Hermetic lots.