L_max = ΔU / (2 * I * R)
L_max = ΔU / (2 * I * (R * cosφ + X * sinφ))
L_max = ΔU / (√3 * I * (R * cosφ + X * sinφ))
ΔU = Voltage drop (V)
I = Current (A)
R = Resistance (Ω / km)
X = Reactance (Ω / km)
L_max = Line length (km)
φ = Phase shift between voltage and current
This tool calculates the maximum cable length that can be used without exceeding the allowable voltage drop and without degrading insulation, based on IEC and NEC standards. It supports DC, single-phase, two-phase, and three-phase systems, including parallel conductors and various temperature ratings.
Current Type: Direct Current (DC), Single-phase AC, Two-phase, or Three-phase (3-wire/4-wire)
Voltage (V): Enter phase-to-neutral voltage for single-phase, or phase-to-phase for polyphase
Load Power (kW or VA): Rated power of the connected equipment
Power Factor (cos φ): Ratio of active to apparent power, between 0 and 1 (default: 0.8)
Wire Size (mm²): Cross-sectional area of the conductor
Parallel Phase Conductors: Conductors with same size, length, and material can be used in parallel; total permissible current is sum of individual core ratings
Voltage Drop (% or V): Maximum allowable voltage drop (e.g., 3% for lighting, 5% for motors)
Conductor Material: Copper (Cu) or Aluminum (Al), affecting resistivity
Cable Type:
Unipolar: 1 conductor
Bipolar: 2 conductors
Tripolar: 3 conductors
Quadrupolar: 4 conductors
Pentapolar: 5 conductors
Multipolar: 2 or more conductors
Operating Temperature (°C): Based on insulation type:
IEC/CEI: 70°C (PVC), 90°C (XLPE/EPR), 105°C (Mineral Insulation)
NEC: 60°C (TW, UF), 75°C (RHW, THHN, etc.), 90°C (TBS, XHHW, etc.)
1.Maximum allowable cable length (meters)
2.Actual voltage drop (% and V)
3.Conductor resistance (Ω/km)
4.Total circuit resistance (Ω)
5.Reference Standards: IEC 60364, NEC Article 215
Designed for electrical engineers and installers to plan wiring layouts and ensure acceptable voltage levels at the load end.
The larger the conductor cross-sectional area, the lower the resistance per unit length, resulting in a smaller voltage drop at the same current. Therefore, a longer cable run is permitted.
Copper has a lower resistivity than aluminum. For the same cross-sectional area, copper cables have lower resistance and less voltage drop, allowing for longer cable runs.
Yes. Multiple conductors in parallel effectively reduce the total circuit resistance and voltage drop, allowing for longer cable runs. However, the parallel conductors must be identical in size, length, and material.
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