Cable Calculations May 2026

A simplified thermal model:

You're likely asking about for a solid conductor (single solid metal wire), as opposed to stranded wire. cable calculations

| AWG | mm² approx | Ampacity (60°C wire) | Ampacity (75°C wire) | Ampacity (90°C wire) | |-----|------------|----------------------|----------------------|----------------------| | 14 | 2.08 | 15 A | 20 A | 25 A | | 12 | 3.31 | 20 A | 25 A | 30 A | | 10 | 5.26 | 30 A | 35 A | 40 A | | 8 | 8.37 | 40 A | 50 A | 55 A | A simplified thermal model: You're likely asking about

Example: 12 AWG solid copper, (R \approx 1.588\ \Omega/1000ft) at 75°C, 100 ft, 20 A: [ V_d = 2 \times 100 \times 20 \times 1.588 / 1000 = 6.35\ V \ (\approx 5.3%\ \texton 120V) ] Aim for < 3%. For very high frequencies (kHz to MHz) → skin effect forces you to use AC resistance: [ R_ac = R_dc \times \frack \cdot r2 ] …but at 60 Hz, for solid wire up to ~4 AWG, (R_ac \approx R_dc). [ I = \sqrt\fracT_max - T_ambR_dc \cdot R_th ]

[ I = \sqrt\fracT_max - T_ambR_dc \cdot R_th ]