Shad Bala (षड्बल) - six-fold planetary strength - is computed by summing six independent components, each measured in Shashtiamshas (virupas). Dividing the total by 60 yields Rupas, which are compared against BPHS-prescribed minimum thresholds to classify each planet as strong, average, or weak.
Positional strength - five sub-components: Uchcha Bala (distance from debilitation point, 0-60), Sapta Vargiya Bala (dignity across 7 divisional charts), Ojayugma Bala (odd/even sign preference), Kendradi Bala (angular 60 / succedent 30 / cadent 15), and Drekkana Bala (decanate preference).
Directional strength - distance from the planet's worst direction (opposite its preferred house). Sun/Mars: 10th; Moon/Venus: 4th; Mercury/Jupiter: 1st; Saturn: 7th. Maximum 60 shashtiamshas when opposite the worst direction.
Temporal strength - six sub-components: Natonnata Bala (day/night birth affinity), Paksha Bala (waxing/waning Moon phase), Tribhaga Bala (lord of birth's day/night third), Vara Bala (weekday lord), Hora Bala (planetary hour lord), and Ayana Bala (declination-based northern/southern strength).
Motional strength - based on speed relative to mean daily motion. Retrograde (vakri) planets receive maximum 60 shashtiamshas. Sun and Moon use Ayana Bala here. Other planets: retrograde=60, near-stationary=15, slow=30, mean=7.5, fast up to 45.
Natural inherent strength - fixed hierarchy from BPHS: Sun=60, Moon=51.43, Venus=42.86, Jupiter=34.28, Mercury=25.71, Mars=17.14, Saturn=8.57 shashtiamshas. Unchanging for every chart.
Aspectual strength - strength received from planets aspecting this planet. Natural benefics (Moon, Mercury, Jupiter, Venus) contribute positive strength; natural malefics (Sun, Mars, Saturn) contribute negative. Special aspects: Mars (4th/8th), Jupiter (5th/9th), Saturn (3rd/10th) at 3/4 weight.
Total Rupas = (Sthana + Dig + Kala + Cheshta + Naisargika + Drik) ÷ 60
Minimum required (BPHS Ch.27): Sun 6.5 r · Moon 6.0 r · Mars 5.0 r · Mercury 7.0 r · Jupiter 6.5 r · Venus 5.5 r · Saturn 5.0 r
Ishta Phala (benefic results) = √(Uchcha Bala × Cheshta Bala)
Kashta Phala (malefic results) = √((60 - Uchcha Bala) × (60 - Cheshta Bala))