Construction & Electrical

Cable size by load calculator

Select the installation country before calculating: South Korea uses KEC-referenced KS tables and the USA uses NEC 2023 reference conditions. Korean sizes use mm²; US sizes use AWG or kcmil. Enter essential values first, then expand installation conditions and calculation details when needed.

MAKE IT SIMPLE

Installation country / rulesLoad power (kW)Power supply

A general-wiring breaker rating candidate is selected automatically.

Installation

Copper · XLPE 90°C · 30°C ambient · 1 circuit. Additional conditions below.

Change site conditions

Enter a breaker rating myselfActual voltage (V)Power factorEfficiency (%; 100 for electrical input power)

InsulationGroupingLoaded circuitsAdditional verified derating factor

Ambient air temperature (°C)

Calculation basis

KEC 232.5.2 references KS C IEC60364-5-52, confirmed 2024-07-31 (identical to IEC Edition 3). Copper only, B2/C, 2/3 loaded conductors, 1.5–300 mm².

Automatic breaker selection gives a general-wiring rated-current candidate, not a specific product or final protection design. Motors, HVAC, welders, fault interrupting capacity and protective coordination require separate selection. The candidate sets are 15–630 A for Korea and 15–600 A for USA; US 10 A special applications are excluded. Thermal/rating reference only. Voltage drop, fault withstand, disconnection, manufacturer/terminal limits and special installation conditions require separate verification. Basis reviewed 21 October 2026.

Check actual installation conditions before selecting a cable.

Result

A QUICK GUIDE

How to use

Choose the installation country independently of the display language. Korea KEC/KS and USA NEC 2023 are separate profiles; verify the locally adopted NEC edition.
Enter load power, supply and installation method. A supported general-wiring breaker rating and cable size candidate are selected automatically. Expand Site conditions to adjust temperature, grouping or power factor, or to enter a verified breaker rating manually.
Read the concise result, or expand Calculation details for correction factors and conditions. Voltage drop, protection coordination, equipment and manufacturer limits require separate verification.
Korea supports copper B2/C 1.5–300 mm². USA supports copper THHN/THWN-2 90°C, 14 AWG–500 kcmil under raceway/cable conditions, with a 60°C termination default, optional verified 75°C terminations, small-wire OCP caps and the selected 125% continuous-load allowance.

Worked examples

Korea · 10 kW electrical input, 380 V three-phase, PF 0.9, copper XLPE B2, 30°C, 1 circuit, automatic breaker

Breaker candidate 20 A; cable 2.5 mm²; allowable ampacity 26 A

Load current is about 16.88 A. Select the supported 20 A rating, then the smallest cable rated at least 20 A under these conditions. Special loads need separate protection selection.

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