South African Wire Thickness Calculator
Estimate the minimum copper conductor size for AC and DC circuits in South Africa based on SANS 10142 voltage drop recommendations. Enter your load, supply and distance to see the nearest standard cable size that keeps voltage drop within limits.
1. Circuit Inputs
Lighting and mixed socket circuits (≤5% drop)
V
A
m
Enter the single run length. The calculator doubles what is needed.
The calculation uses copper resistivity of 0.018 Ω·mm²/m and keeps the voltage drop within 5.0% of the selected supply voltage.
2. Recommended Cable Size
Required cross-sectional area
1.25 mm²
Use at least a 1.5 mm² copper conductor. This keeps the voltage drop around 4.17%.
Voltage drop at this size
9.6 V
SANS limit (5.0%)
11.5 V
How we calculate
A = (k × ρ × I × L) / ΔV, where k = 2.000, ρ = 0.018 Ω·mm²/m, I = 20 A, L = 20 m and ΔV is the allowable drop based on the selected load type.
Typical Voltage Drop Limits (SANS 10142 guidance)
| Load type | Max drop | Examples |
|---|---|---|
| General purpose circuits | 5.0% | Lighting and mixed socket circuits (≤5% drop) |
| Motors / HVAC | 3.0% | Motors, compressors and pumps (≤3% drop) |
| Sensitive electronics | 2.0% | UPS, control circuits and instrumentation (≤2% drop) |
Standard Copper Cable Sizes (mm²)
1.52.54610162535507095120150185240
This tool provides guidance only. Always verify cable sizing against the full requirements of SANS 10142-1, considering temperature, grouping, installation method and protective device ratings before installation.