Formula For Cable Size Calculation Fixed Jun 2026

The most critical constraint is thermal. When current ($I$) flows through a conductor of resistance ($R$), heat is generated at a rate of $I^2R$ (Joule's law). The cable must dissipate this heat without exceeding its insulation's maximum permissible temperature. The governing formula is deceptively simple:

Where:

$$I = \fracPV \times \textPF$$

Then, verify this size against current-carrying capacity tables. formula for cable size calculation

Ib=PV×PFcap I sub b equals the fraction with numerator cap P and denominator cap V cross cap P cap F end-fraction The most critical constraint is thermal