Voltage drop calculator (resistive estimate)

Circuit current (A)

One-way length

Length unit Feet (ft) Meters (m)

Conductor resistance per length

Resistance unit Ohms per foot (Ω/ft) Ohms per meter (Ω/m)

Loop factor Default 2 = go-and-return for this two-conductor model.

Nominal supply voltage (V)

Calculate Copy summary

— Enter current, length, Ω/length, and nominal voltage.

• 20 A · 100 ft · 0.0005 Ω/ft · factor 2 · 120 V → Rloop 0.1 Ω · Vd 2 V · 1.666…% · 118 V at load
• Rloop = L × (Ω/length) × loopFactor · Vd = I × Rloop
• Vload = Vnominal − Vd (rejected if Vload is negative)

Simplified two-conductor resistive estimate. Default loop factor 2 means go-and-return when length is one leg. You supply Ω/ft or Ω/m from an external source. Does not select AWG, ampacity, breakers, three-phase impedance, or claim NEC compliance.

Rloop = L × (Ω/length) × loopFactor (default 2); Vd = I × Rloop; Vload = Vnom − Vd. You supply Ω/ft or Ω/m from an external source. Not AWG selection, ampacity, 3φ impedance, or NEC.