Free calculator for Belgium
Calculate voltage drop and cable cross-section
Check a selected cross-section or estimate a preliminary size, with no sign-up required.
Cable run data
Do not enter the return path; the formula already accounts for it.
Preliminary cross-section
2.5 mm²
Calculation inputs
Supply network: 1x230V
Circuit: Single-phase
Load: 16 A
Cable length, one-way: 30 m
Conductor material: Copper
Circuit breaker: 16 A
Final-circuit type: Other final circuit
Power factor cos φ: 0.95
Active power: 3.5 kW
Nominal voltage: 230 V
Calculated current
16 A
3.5 kW
Voltage drop
2.78 %
Voltage at load
223.62 V
Minimum from protection and circuit type: 2.5 mm²
All cross-sections compared
Limit 5 %
- suitable
- meets both the limit and the breaker minimum
- too thin for the breaker
- voltage drop is fine, but too thin for the breaker
- voltage drop too high
- voltage drop above the limit
Checked are the voltage drop and the minimum from Table 4.11. Installation method, grouping and ambient temperature can require a larger cross-section.
2.5 mm² stays within the limit up to 54 m.
Compare cross-sections
| Cross-section | ΔU | Voltage at load | Reaches | Protection |
|---|---|---|---|---|
| 1.5 mm² | 10.64 V · 4.63 % | 219.36 V | 32 m | too thin |
| 2.5 mm² | 6.38 V · 2.78 % | 223.62 V | 54 m | suitable |
| 4 mm² | 3.99 V · 1.73 % | 226.01 V | 86 m | suitable |
| 6 mm² | 2.66 V · 1.16 % | 227.34 V | 130 m | suitable |
| 10 mm² | 1.6 V · 0.69 % | 228.4 V | 216 m | suitable |
| 16 mm² | 1 V · 0.43 % | 229 V | 346 m | suitable |
| 25 mm² | 0.64 V · 0.28 % | 229.36 V | 540 m | suitable |
| 35 mm² | 0.46 V · 0.2 % | 229.54 V | 757 m | suitable |
| 50 mm² | 0.32 V · 0.14 % | 229.68 V | 1,081 m | suitable |
Source and limits
Preliminary check based on AREI/RGIE Book 1 (version effective since 1 April 2026) and documented rules of good practice. This is not a complete cable design.
Not checked: installation method, grouping, temperature, reactance, short-circuit withstand, disconnection conditions, terminals and manufacturer data.
What does this tool calculate?
The protective device and circuit type set an initial minimum. Length and load can require a larger cross-section because of voltage drop. The larger result becomes the preliminary size.
Frequently asked questions
Which network type do I have?
1×230 V is the usual single-phase domestic connection. 3N~400/230 V with neutral is today’s three-phase connection. 3×230 V without neutral appears in older Belgian installations; the permitted voltage drop is smaller in volts there because it refers to 230 V rather than 400 V.
When does the tool use 400 V?
Only for a three-phase circuit, because 400 V exists only between two line conductors. A single-phase final circuit always uses 230 V — against neutral on 1×230 V and 3N~400/230 V, between two line conductors on 3×230 V. The formula differs too: factor 2 single-phase for the return conductor, √3 three-phase.
Is the length one-way or there and back?
Enter the one-way distance from the distribution board to the load. The single-phase factor of 2 accounts for the return path.
Are 3% and 5% literal AREI limits?
No. AREI/RGIE 5.2.5 refers to the rules of good practice. PlanElec uses the documented 3% for lighting and 5% for other final circuits as preliminary thresholds.
Is the result AREI compliant?
The result checks only part of cable sizing and does not replace a complete design or inspection.