How to calculate cable cross-section size?

Cable cross-section is calculated using A = (k × ρ × I × L) / V_drop, where k is a system factor (2 for single-phase/DC, √3 for three-phase), ρ is conductor resistivity, I is current in amps, L is one-way cable length in meters, and V_drop is the allowable voltage drop in volts.

Why is voltage drop important in cable sizing?

Excessive voltage drop causes equipment to receive less than rated voltage, leading to poor performance, overheating of motors, dimming of lights, and potential equipment damage. Most standards recommend limiting voltage drop to 3-5% of supply voltage.

What is the difference between copper and aluminum cables?

Copper has lower resistivity (0.0175 Ω·mm²/m) than aluminum (0.0283 Ω·mm²/m), meaning copper cables can carry the same current with a smaller cross-section. However, aluminum is lighter and cheaper. Aluminum requires about 1.6× the cross-section of copper for the same current capacity.

What are standard cable sizes?

Standard cable cross-sections per IEC 60228 are: 0.75, 1.0, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, and 300 mm². The calculated cross-section should always be rounded up to the next standard size.

How to convert AWG to mm²?

Common conversions: 14 AWG ≈ 2.08 mm², 12 AWG ≈ 3.31 mm², 10 AWG ≈ 5.26 mm², 8 AWG ≈ 8.37 mm², 6 AWG ≈ 13.3 mm², 4 AWG ≈ 21.2 mm², 2 AWG ≈ 33.6 mm², 1/0 AWG ≈ 53.5 mm², 4/0 AWG ≈ 107 mm².

免費工程工具

電纜截面積計算器

根據電流、電纜長度、電壓及允許電壓降，計算正確的線徑 (mm²)。自動向上取整至最接近的 IEC 標準規格。

IEC 60228 Cu & Al mm² & AWG

電流 (A)

電纜長度 (m, 單程)

電壓 (V)

系統類型

最大電壓降 (%)

導體材質

快速預設

結果

所需標準電纜規格

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計算截面積 (精確值)

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實際電壓降 (標準規格)

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電壓降百分比

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AWG 等效規格

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電纜截面積公式

為使電壓降保持在允許範圍內，所需的最小導體截面積為：

k — 系統係數：單相交流與直流為 2，三相交流為 √3
ρ — 導體電阻率 (Ω·mm²/m)：Cu = 0.0175，Al = 0.0283
I — 電流 (A)
L — 單程電纜長度 (m)
V_電壓降 — 允許電壓降 (V)

允許電壓降

實際電壓降

選定標準電纜規格 A_std 後：

標準電纜規格 (IEC 60228)

mm²	AWG (約)	mm²	AWG (約)
0.75	18 AWG	25	4 AWG
1.0	17 AWG	35	2 AWG
1.5	15 AWG	50	1/0 AWG
2.5	13 AWG	70	2/0 AWG
4	11 AWG	95	3/0 AWG
6	9 AWG	120	4/0 AWG
10	7 AWG	150	300 MCM
16	5 AWG	185	350 MCM

實務範例

範例 — 單相 230V 電路

已知： I = 10 A, L = 30 m, V = 230 V, 最大壓降 = 3%, 銅

V_{drop(allowed)} = 230 × 3/100 = 6.9 V

A = 2 × 0.0175 × 10 × 30 / 6.9 = 1.52 mm²

標準規格： 2.5 mm² （向上取整）

實際 V_電壓降 = 2 × 0.0175 × 10 × 30 / 2.5 = 4.2 V = 1.83%

⚠️ 注意： 此計算器僅根據電壓降來計算電纜規格。請務必確認所選電纜規格亦符合當地電氣法規（如 IEC 60364、NEC）的載流量（安培容量）要求。