Free engineering tool
Voltage Drop Calculator
Calculate voltage drop and cable losses for DC, single-phase AC, and three-phase circuits.
Calculator
Distance from source to load, not the out-and-back conductor length.
Not ambient temperature. Resistance is corrected from 20°C; the actual cable's permitted temperature may be far below this input range.
DC conductor resistance from the datasheet at 20°C. Leave blank for the material-and-area approximation.
0.08 Ω/km is a common approximation for low-voltage cables.
Applies only to this cable segment. Budget upstream cables and connections separately; current project, equipment, and code requirements govern.
Voltage drop: 5.332 V
Calculated values
Voltage drop
5.332 V
Magnitude is within the entered design reference
Voltage drop
1.333 %
≤ 3 %
Estimated load voltage
394.668 V
DC conductor resistance at operating temperature
2.0991 Ω/km
One-way conductor resistance
0.10496 Ω
Resistive cable loss
322.43 W
Maximum one-way length at design limit
112.52 m
Required minimum cross-section
4.4 mm²
Round up to the next standard size and verify ampacity separately.
Formula and calculation method
This calculator estimates steady-state voltage drop in DC, single-phase AC, and balanced three-phase circuits. Length is always one-way; the appropriate return-path or √3 factor is applied automatically.
DC: ΔU = 2 × I × R × L
Single-phase: ΔU ≈ 2 × I × L × (R cos φ ± X sin φ)
Three-phase: ΔU ≈ √3 × I × L × (R cos φ ± X sin φ)
Cable loss: 2 × I²RL (DC/1φ) or 3 × I²RL (3φ)
Assumptions and limitations
- Material values use OVE conductivity at 20°C and temperature coefficients to correct for the entered conductor operating temperature. A manufacturer R20 value takes precedence.
- The reactance term is added for lagging loads and subtracted for leading loads. A negative ΔU is reported as voltage rise; the design limit uses its magnitude. 0.08 Ω/km is only a fallback when cable data is unavailable.
- The entered limit is an editable design reference for this cable segment only. Upstream cables and connections must be added to the overall budget; current OVE, project, and equipment requirements govern.
- This tool does not verify ampacity, protection, short-circuit withstand, insulation, or installation conditions. Those checks remain necessary for cable sizing.
Technical sources
Formulas and conventions were checked against these primary and manufacturer references.