The current travels out and back
A 50 m one-way run has 100 m of conductor in a matching two-wire loop. At 5 Ω/km, the cable resistance is 0.5 Ω. With 10 A, that produces 5 V of drop and 50 W of resistive loss.
Add connection resistance when it is not already included in the measurement. A measured loop value already includes both directions, so it is used once. The geometric method uses your supplied resistivity, conductor area and reference condition.
This calculator estimates resistive DC loss at a constant current. It does not choose cable ampacity, protective devices or an allowable code limit. Equipment may draw a different current when delivered voltage changes.
