षड्बल Ṣaḍbala

Shadbala is the classical six-fold strength score: a planet's power measured from its position, direction, time of birth, motion, natural rank, and aspects — the number behind 'strong' and 'weak'. 'Shad-bala' means 'six strengths', and the idea is plain: whether a planet can actually deliver what it promises depends not on one thing but on many, so the tradition measures six and adds them up. A planet earns points for sitting in a good sign (positional strength), for standing in the right quarter of the sky (directional), for the time and circumstances of birth (temporal), for its motion — where a retrograde planet scores high — for its natural rank among the planets, and for the aspects it receives. The total, counted in units called rupas, is checked against a minimum each planet is expected to reach: one that meets its requirement is fit to give its results, while one that falls short may promise much and deliver little. It is the arithmetic behind the everyday words 'strong' and 'weak', and it is why two planets in the very same sign can perform so differently.