Cross-section calculation cable

Yes, cross-section and gauge are synonyms. Both refer to the cross-sectional area of the current-carrying conductor in mm². In IEC 60364 and IEC standards, the official term is 'cross-section', while in common speech and some older sources, 'gauge' is used. In both cases, the same values are meant: 1.5 mm², 2.5 mm², 4 mm², 6 mm², 10 mm², 16 mm², etc.

First calculate the operating current: I = P / (U × cosφ). For single-phase 220V and resistive load (cosφ=1): I = P (kW) × 4.55. Example: a 2 kW water heater → I ≈ 9 A → cross-section 1.5 mm² (copper, in wall, permissible current 19 A — with margin). An electric stove 7 kW → I ≈ 32 A → cross-section 6 mm². The calculator performs this calculation automatically — enter power in kW, get the recommended cross-section verified by two criteria: permissible current and voltage drop.

For the incoming cable — 6 mm² (copper), if longer than 25 m from the meter — 10 mm². For socket circuits — 2.5 mm² (MCB B16 or C16), for lighting — 1.5 mm² (MCB B10). Values for installation in wall (method A2) per the app's reference table.

A cable in a wall (A2) is surrounded by masonry and dissipates heat poorly, so its permissible current is lower. For example, a 2.5 mm² Cu cable in a wall can carry 21 A, while surface-mounted (C) — 27 A. If cross-section is chosen without considering the installation method, the cable may overheat even under normal load.

On long runs — from 30–50 m and beyond. For example, to power a garage 40 m away with 5 kW load, 2.5 mm² is sufficient for current, but 6 mm² is needed for voltage drop. If this criterion is ignored, equipment receives reduced voltage, shortening its lifespan.

For internal wiring, IEC 60364 recommends copper cable. Copper has lower resistivity (0.0225 vs 0.036 Ω·mm²/m at 70 °C), can carry higher current for the same cross-section, is more flexible and durable. Aluminium is suitable for large incoming cables (from 16 mm²).

For an electric stove 7–8 kW (single-phase) — cable 6 mm² (Cu) with MCB C32. For a built-in oven up to 3.5 kW — a separate circuit 2.5 mm² with MCB C16. Both for installation in wall. Always run a separate line from the distribution board.

Calculate the operating current: I = P / (U × cosφ) for single-phase or I = P / (√3 × U × cosφ) for three-phase. Find in the ampacity table a cross-section whose permissible current ≥ I. In wall (A2), permissible current is 20–30% lower than surface-mounted (C).

The basic logic can be used: cosφ = 1, coefficient k = 2 always (two conductors — plus and minus). Permissible current tables for DC cables differ slightly from IEC AC tables. For battery systems and solar panels, check against the manufacturer's DC cable specifications.