Engineering resources

Cable size reference and quick sizing helper

Quick references for site engineers and purchase teams. Values are indicative. Confirm final selections with manufacturer data and a qualified engineer.

Reference

Current-carrying capacity: 1.1 kV PVC, 3 / 3.5 / 4 core armoured

Indicative values compiled from widely published manufacturer tables based on IS 1554 (Part 1) / IS 3961 rating methods. Ground: laid direct at 30 °C ground temperature, soil thermal resistivity 1.5 K·m/W. Air: 40 °C ambient, single circuit, no grouping.

Find size (sq mm) or current (A)

ConductorBothCopperAluminium

17 sizes

Indicative current ratings in amperes and voltage drop by conductor size
Size (sq mm)	Copper			Aluminium
Size (sq mm)	Ground (A)	Air (A)	mV/A/m	Ground (A)	Air (A)	mV/A/m
1.5	18	15	25	–	–	–
2.5	24	21	15	19	16	25
4	32	27	9.5	25	21	15.5
6	40	35	6.4	31	27	10.4
10	54	45	3.8	42	35	6.2
16	69	60	2.4	54	47	3.9
25	90	82	1.5	70	64	2.5
35	110	100	1.1	86	78	1.8
50	132	123	0.81	103	96	1.35
70	163	152	0.57	127	119	0.93
95	197	187	0.42	154	146	0.68
120	224	216	0.35	175	169	0.55
150	251	246	0.29	196	192	0.45
185	284	282	0.24	222	220	0.37
240	326	333	0.21	255	260	0.3
300	365	378	0.19	285	295	0.26
400	410	435	0.17	320	340	0.22

Indicative only. Ratings vary by manufacturer, construction, installation method, grouping and ambient conditions. Always confirm with the manufacturer's data sheet and a qualified electrical engineer.

XLPE (IS 7098 Pt 1) cables of the same size typically carry around 20–30% more current. Use the manufacturer's XLPE table. Approximate three-phase voltage drop in mV per ampere per metre at conductor operating temperature. Single-phase drop is about 1.15 times the three-phase value. Apply derating factors for grouping, ambient temperature and depth of laying.

Calculator

Cable size helper

Enter the load and route length for a first-cut size from the table above, checked against your allowable voltage drop.

Load current

– A

Size by current: –
Suggested (with voltage drop): –

Indicative only. Consult a qualified electrical engineer. This helper ignores derating for grouping and ambient temperature, motor starting current, short-circuit withstand and earth-fault loop impedance, all of which can require a larger cable.

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