Copper vs aluminium cable calculator

Before swapping copper for aluminium to save cost, see what you give up. Enter the cable length, area and operating temperature — read DC resistance, voltage drop and weight for both metals, plus the aluminium size that matches copper's resistance.

Cable parameters

Cable length

One-way conductor length

Cross-sectional area

mm² conductor area

Operating temperature

°C — resistivity rises with temperature

Load current (optional)

For the voltage-drop comparison

Metal

Resistivity at 20°C: 0.01724 Ω·mm²/m for copper.

DC resistance: 0.1724Ω
Voltage drop at load (one-way): 5.52V
Conductor weight: 9.0kg

Copper vs aluminium trade-off

Aluminium resistance vs copper: 1.64×higher
Weight saving with aluminium: 69.9%
Aluminium size for same resistance: 16.4mm²

Aluminium weighs about 70 % less per metre but has ~1.6× the resistance of copper, so an aluminium conductor needs a roughly 60 % larger cross-section to carry the same current with the same drop. The trade is lighter, cheaper cable against larger termination hardware and corrosion management.

Cost to buy the run

Copper price

$ per kg of conductor

Aluminium price

$ per kg of conductor

Copper run cost: $107.52(9.0 kg)
Aluminium run cost: $17.70(4.4 kg)
Cost saving with aluminium: 83.5%

The aluminium cost uses the larger area that matches copper's resistance — so the saving is net of upsizing. Conductor prices are market-driven; enter your real per-kg figures (e.g. from an exchange or supplier quote) for a meaningful comparison.

Pick the right termination

Terminals are metal-specific: aluminium cable lugs and copper lugs are not interchangeable, and mixing metals without a bimetallic joint invites galvanic corrosion.

Frequently asked questions

How much bigger does an aluminium conductor need to be to match copper's resistance?

At the same length and temperature, aluminium has about 1.6× the resistance of copper, so it needs roughly a 60% larger cross-section. The calculator works it out directly: aluminium size = copper area × (R_al ÷ R_cu), and it uses that upsized aluminium in the cost comparison.

How is cable resistance calculated and corrected for temperature?

Resistance uses R = ρ·L/A with temperature-corrected resistivity ρ = ρ₂₀ × (1 + α·(T − 20)). Copper uses ρ₂₀ = 0.01724 Ω·mm²/m with α = 0.00393 /°C, and aluminium 0.02826 Ω·mm²/m with α = 0.00403 /°C — so a 10 mm² copper cable at 20 °C reads about 0.172 Ω for 100 m.

Why is the aluminium weight and cost saving not as big as it first looks?

Aluminium weighs about 70% less per metre, but the cost saving is computed on the larger area that matches copper's resistance — that is why the calculator's cost row is net of upsizing. It also uses weight from density 8.96 g/cm³ (Cu) and 2.70 g/cm³ (Al) for the bare conductor only.

How it works

Resistance uses R = ρ·L/A with temperature correction: ρ = ρ₂₀ × (1 + α·(T − 20)) — copper ρ₂₀ = 0.01724 Ω·mm²/m, aluminium ρ₂₀ = 0.02826 Ω·mm²/m. Weight uses density 8.96 g/cm³ (Cu) and 2.70 g/cm³ (Al). This is a DC model; skin effect, inductance and jacket weight are not included.

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