How To Calculate Cable Sizes [portable]

If the cross-sectional area calculated here is larger than the area selected in Step 2, you must use the larger size.

References: IEC 60364-5-52, BS 7671 (UK), NEC Article 310 (US), AS/NZS 3008 (Australia).

[ I_z \geq I_b ]

$$V_d = \frac\sqrt3 \times I \times L \times \rhoA$$

To size a cable correctly, you must check it against three distinct criteria: how to calculate cable sizes

( V_d = \frac2 \times L \times I_b \times R_ac1000 ) (in volts)

Despite 2.5 mm² handling the current, voltage drop forces 6 mm² cable for this 40m run. If the cross-sectional area calculated here is larger

If calculated ( V_d ) exceeds limit, until drop is acceptable. Voltage drop almost always dictates final size for long runs.

Selecting the correct cable size is critical for electrical safety, system efficiency, and regulatory compliance. An undersized cable overheats, causes voltage drops, and risks fire; an oversized cable is economically wasteful. This guide covers the five mandatory factors for accurate sizing. If calculated ( V_d ) exceeds limit, until