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Wire & Cable Size Calculator

Size copper conductors for ampacity (current-carrying capacity) and permissible voltage drop in one pass, using correction factors consistent with IS 732 and IEC 60364-5-52. Enter the circuit details below — results update as you type.

Circuit Input

System

Load input as

Design load current, I_b (A)

Load (kW)

Power factor

For motor loads, include efficiency below; for resistive/lighting loads set efficiency to 1.

Efficiency, η

System voltage (V)

Route length, one-way (m)

Insulation PVC (70°C) XLPE (90°C)

Installation method Enclosed in conduit / trunking Clipped direct / free air Buried direct in ground

Ambient temperature (°C) 25 30 35 40 45 50 55 60

Circuits grouped together 1 2 3 4 5 6 7–9 10+

Max. allowable voltage drop (%) 3% — lighting circuit 5% — power circuit 2.5% — sensitive / long feeder

Recommended Cable

6mm²

Ampacity-governed

Copper conductor, PVC insulated

Load exceeds the largest standard size modelled here (240 mm²). Consider parallel runs or specialist design.

How this calculator sizes a cable (IS 732 / IEC 60364-5-52 method)

Correct cable sizing is governed by two independent checks, and the final selection is whichever demands the larger cross-section:

1. Current-carrying capacity (ampacity). The tabulated ampacity of a cable — published in IS 732 and IEC 60364-5-52 for standard installation methods — must be de-rated for ambient temperature and for grouping with other loaded circuits. The corrected ampacity must equal or exceed the design load current, I_b.

2. Voltage drop. Even a cable with adequate ampacity can produce excessive voltage drop over long runs, degrading equipment performance. This tool checks the resulting drop against the commonly used limits of 3% for lighting and 5% for power circuits (final sub-circuit, per typical IS 732 / IEC guidance), and upsizes the conductor if required.

Where the ampacity check and the voltage-drop check select different sizes, the calculator reports the larger of the two as the governing constraint.

Derating factors used

Ambient temperature correction (PVC reference 30°C): factors fall from about 1.03 at 25°C to 0.50 at 60°C, reflecting reduced heat dissipation as ambient rises.

Grouping correction: multiple loaded circuits bundled together restrict heat dissipation; the correction factor drops from 1.00 for a single circuit to roughly 0.50 for ten or more grouped circuits.

Insulation type: XLPE-insulated cable operates at a 90°C conductor limit versus 70°C for PVC, giving it a higher base ampacity for the same cross-section — modelled here as an approximate uplift factor.

Assumptions & limitations

Ampacity and millivolt-drop-per-amp-metre figures used here are indicative reference values consistent with commonly published IS 732 / IEC 60364-5-52 tables for single-core PVC/XLPE insulated copper cable. They are not a substitute for the current edition of the standard or a specific manufacturer's cable data sheet.

This tool does not check short-circuit thermal withstand, protective device coordination, or earth fault loop impedance — all of which must be verified separately by a competent engineer before finalising a design.

Reference calculator for preliminary cable sizing — verify final selection against the current IS 732 / IEC 60364-5-52 edition and manufacturer cable data before use in a design submission. Built for wazipoint.com.