Voltage drop calculator for a cable
A long or thin cable loses some voltage. Type the current, the length and the wire size to see how much.
Result
7.2 VVoltage drop
- As % of the voltage
- 3.13%
- Voltage at the end of the cable
- 222.8 V
- Resistivity used
- 0.0225 Ω·mm²/m
- For information: many national rules aim for at most 3% for lighting and 5% for other uses (e.g. France NF C 15-100). Rules differ by country.
Inputs
- Circuit type
- Single-phase or DC
- Supply voltage
- 230
- Current
- 16
- Cable length (one way)
- 25
- Wire cross-section
- 2.5
- Cable metal
- Copper
How it is calculated
Single-phase or DC: ΔU = 2 × L × I × ρ ÷ S (current goes out and back).
Result
Voltage drop
- As % of the voltage
- 3.13%
- Voltage at the end of the cable
- 222.8 V
- Resistivity used
- 0.0225 Ω·mm²/m
How it is calculated
- Single-phase or DC: ΔU = 2 × L × I × ρ ÷ S (current goes out and back).
- Balanced three-phase: ΔU = √3 × L × I × ρ ÷ S.
- ρ = 0.0225 Ω·mm²/m for copper and 0.036 for aluminium (warm cable).
- Percentage = ΔU ÷ voltage × 100.
Example
16 A over 25 m of 2.5 mm² copper at 230 V: 2 × 25 × 16 × 0.0225 ÷ 2.5 = 7.2 V, so 3.1%.
Good to know
- For information only: it does not check that an electrical installation meets the rules.
- Cable reactance and power factor are ignored (simplified method).
- For any electrical work, call a qualified electrician.
Frequently asked questions
What is this tool used for?
A long or thin cable loses some voltage. Type the current, the length and the wire size to see how much.
How is the result calculated?
Single-phase or DC: ΔU = 2 × L × I × ρ ÷ S (current goes out and back).
What should I check before using the result?
For information only: it does not check that an electrical installation meets the rules.