Voltage Drop Calculator – Aluminum Wire
Aluminum has about 64% higher resistivity than copper — you need a larger cross-section to match copper's voltage drop performance. Standard for service entrance cables, feeders, and utility distribution where weight and cost matter more than conductor size. Uses IEC aluminum resistance values (ρ = 2.82×10⁻⁸ Ω·m).
This calculator provides estimates only. Always consult a qualified electrician and verify against local wiring regulations before installation.
Calculate Voltage Drop (Aluminum)
Voltage Drop Results
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Voltage Drop (V)
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Voltage at Load (V)
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Aluminum Wire Resistance Reference
| Wire Size (mm²) | Al Resistance (mΩ/m) | Cu Equivalent (mm²) | Ampacity (A) |
|---|---|---|---|
| 10 mm² | 3.08 | 6 mm² Cu | 44 A |
| 16 mm² | 1.91 | 10 mm² Cu | 59 A |
| 25 mm² | 1.20 | 16 mm² Cu | 79 A |
| 35 mm² | 0.868 | 25 mm² Cu | 98 A |
| 50 mm² | 0.641 | 35 mm² Cu | 118 A |
| 70 mm² | 0.443 | 50 mm² Cu | 150 A |
| 95 mm² | 0.320 | 70 mm² Cu | 183 A |
| 120 mm² | 0.253 | 95 mm² Cu | 213 A |
Aluminum resistivity ≈ 2.82 × 10⁻⁸ Ω·m — about 64% higher than copper (1.72 × 10⁻⁸ Ω·m).
Frequently Asked Questions
How much more voltage drop does aluminum have compared to copper?
Aluminum has 64% higher resistivity than copper. For the same wire size, current, and length, aluminum produces 64% more voltage drop. To achieve the same voltage drop as copper, you need aluminum approximately 1.6× larger in cross-section. Example: 16mm² copper ≈ 25mm² aluminum in resistance and voltage drop performance.
When is aluminum wiring used?
Aluminum is widely used for: (1) Service entrance cables and utility feeders — aluminum is standard here, lighter and cheaper than copper at large sizes. (2) Large commercial and industrial feeders — 70mm²+ where aluminum's weight and cost advantage is significant. (3) Overhead distribution lines — virtually all utility lines are aluminum (ACSR). For branch circuit wiring (small gauges) in homes, copper is strongly preferred.
Is aluminum wiring safe?
For large service cables and feeders: yes, when properly terminated with compatible lugs and anti-oxidant compound — this is standard practice. For old small-gauge aluminum branch circuits (installed 1965–1973): higher risk due to connection issues at outlets, switches, and panel breakers. These should be assessed by an electrician and either pigtailed with copper or have all devices replaced with CO/ALR-rated types.