⚡
ElectroBoard/Tools/Cable cross-section calculation
Open constructor →
🔌 CALCULATOR

Cross-section calculation cable

Online cable cross-section calculator by power and current according to IEC 60364 and IEC 60364-5-52 standards. Considers installation method, conductor material, and permissible voltage drop.

⚙️ Input data

Total connected load
Residential: 0.95 · Motors: 0.7–0.85
From panel to load
IEC: up to 5% (recommended ≤3%)

📊 Result

⚡
Calculated current
23.9 A
🔌
Recommended cross-section
2.5 mm²
Permissible current: 24 A (method B2)
📉
Voltage drop
3.91 %
8.61 V over 20 m
⚠️
Voltage drop at tolerance limit
Consider increasing the cross-section or reducing the line length.

How to calculate cable cross-section?

Proper selection of cable cross-section is the basis of safe electrical wiring. A cable that is too thin overheats, which can lead to fire. One that is too thick results in unnecessary material costs.

Cable cross-section is selected based on two criteria: permissible current (according to IEC 60364-5-52 and IEC 60364) and permissible voltage drop (usually up to 5%, recommended up to 3% for lighting circuits).

Permissible current depends on the installation method: a cable in a wall duct (A2) dissipates heat worse than a cable laid openly on a wall (C), so the permissible current is lower. A copper cable can carry more current than an aluminium cable of the same cross-section.

This calculator automatically selects the standard cable cross-section considering both criteria, installation method, and conductor material.

Cable cross-section calculation formula

By criterion allowable current — cross-section is selected from the IEC 60364-5-52 table depending on the installation method and material.

By criterion voltage drop: S = ρ × k × L × I / (U × ΔU%/100), where S — cross-section (mm²), ρ — resistivity (Cu: 0.0175, Al: 0.028 Ω·mm²/m), k = 2 for single-phase or √3 for three-phase, L — length (m), I — current (A), U — voltage (V), ΔU% — permissible voltage drop.

Example: line 40 m, 5 kW (220V, 1ph), Cu, ΔU≤5%. Current: 5000/(220×0.95) ≈ 23.9 A → by current, 4 mm² needed (27A). By voltage drop: S = 0.0175×2×40×23.9/(220×0.05) = 3.05 mm² → standard 4 mm². Result: 4 mm².

Frequently asked questions about cable cross-section

Is 'cable cross-section' the same as 'cable gauge'?
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.
How to calculate cable cross-section based on load power?
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.
What cable cross-section is needed for an apartment with single-phase supply up to 10 kW?
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 IEC 60364-5-52.
Why does the installation method affect cable cross-section selection?
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.
When does voltage drop determine the cross-section rather than permissible current?
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.
Copper or aluminium — which to choose for internal wiring?
For internal wiring, IEC 60364 recommends copper cable. Copper has lower resistivity (0.0175 vs 0.028 Ω·mm²/m), can carry higher current for the same cross-section, is more flexible and durable. Aluminium is suitable for large incoming cables (from 16 mm²).
What cable is needed for an electric stove or oven?
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.
How to select cable cross-section based on load current?
Calculate the operating current: I = P / (U × cosφ) for single-phase or I = P / (√3 × U × cosφ) for three-phase. Find in the IEC 60364-5-52 table a cross-section whose permissible current ≥ I. In wall (A2), permissible current is 20–30% lower than surface-mounted (C).
Is this calculator suitable for DC cable calculation?
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.

Related tools

🛡
MCB selection by load
Breaker rating and trip curve selection (B/C/D) with coordination and selectivity check.
→
📉
Voltage drop calculator
Voltage drop calculation in cable with visualization and cross-section comparison.
→
⚡
Converter W ↔ A ↔ V
Convert watts to amps for 1ph, 3ph and DC grids. Cos φ, recommended MCB and cable cross-section.
→
← All tools (13)

Design electrical panels online

ElectroBoard — electrical panel designer with automatic validation per IEC 60364, load calculation, and PDF export. Free.

Create a panel for free →