Conservative AC/DC mm² from voltage drop and heating.
Default example: 12 V DC, 5 A, 5 m one-way copper at 3% drop → 4 mm² (≈ 11 AWG).
Can be added as standalone app and used offline.
Not a substitute for an electrician or national wiring rules.
Recommended CSA
4 mm²
≈ 11 AWG
Voltage drop is the limiting check.
Calculation details
Conductor
copper
Nearest AWG
11 AWG (4.17 mm²)
Governing check
voltage drop
Voltage-drop size
4 mm²
Heating size
0.75 mm²
S min (calculated)
3.083 mm²
Actual ΔU
0.278 V (2.31 %)
ΔU limit
0.36 V (3 %)
Ampacity of result
35 A (tabulated)
ρ (70 °C)
22.2 mΩ·mm²/m
Method
Standard sizes: IEC 60228 (0.75–240 mm²).
AWG equivalent: nearest ASTM B258 conductor area (then kcmil above
4/0). Pick the gauge that minimises |SAWG − SIEC|.
Example: 4 mm² → 11 AWG (4.17 mm²), not 12 AWG (3.31 mm²). This is
an area match, not an NEC ampacity size.