Conductor tension is calculated using complex formulas that consider the conductor's weight, span length, temperature, and external loads (wind and ice). The common parabolic approximation formula for sag is S = (wL²) / (8T), where S is the sag, w is the conductor's weight per unit length, L is the span length, and T is the tension. Specialized software and stringing charts are used to determine the correct tension for various conditions to ensure the conductor's safety factor is never exceeded.