SWG to mm Conversion Table

Complete Standard Wire Gauge to millimetres reference for Indian wire buyers, engineers and specifiers. SWG 0 to SWG 40 with diameter, cross-section area, and weight per metre for copper, aluminium, GI and steel wire.

Quick Reference � Three Gauges to Remember

CONSTRUCTION BINDING

SWG 16

1.63 mm

MOTOR WINDING

SWG 18

1.22 mm

EARTHING CONDUCTOR

SWG 10

3.25 mm

SWG to mm Conversion Table � Full Range (SWG 0 to SWG 40)

This table lists every standard SWG gauge with the equivalent diameter in millimetres, the nominal cross-section area, and the weight per metre for the three most common wire materials. Use this reference when specifying wire for electrical, construction, fencing, winding or fabrication applications.

SWG	Diameter (mm)	Cross-Section (mm�)	Cu kg/km	Al kg/km	GI/Steel kg/km	Common Uses
0	8.229	53.19	472.9	143.6	417.5	Heavy earthing, bus bar, large overhead conductors
1	7.620	45.60	405.4	123.1	358.0	Heavy earthing, overhead ground wire
2	7.010	38.60	343.2	104.2	303.0	Heavy earthing conductors, ACSR steel core
3	6.401	32.18	286.1	86.9	252.6	Substation earthing, transformer neutral
4	5.893	27.27	242.4	73.6	214.1	Structural binding, heavy fencing, ACSR
5	5.385	22.77	202.4	61.5	178.7	Medium construction, fencing, cable armour
6	4.877	18.68	166.1	50.4	146.6	Overhead ground wire, gabion lacing, fencing
7	4.470	15.70	139.6	42.4	123.2	General fencing, overhead lines, earth grid
8	4.064	12.97	115.3	35.0	101.8	Chain-link fencing, heavy binding, springs
9	3.658	10.51	93.4	28.4	82.5	Binding wire, mesh, overhead earth conductor
10	3.251	8.302	73.8	22.4	65.2	Main earthing conductor, bus bar links, LV lines
11	2.946	6.818	60.6	18.4	53.5	Medium earthing, transformer winding
12	2.642	5.481	48.7	14.8	43.0	Transformer winding (large), springs, mesh
13	2.337	4.289	38.1	11.6	33.7	Fencing wire, binding, medium fabrication
14	2.032	3.243	28.8	8.76	25.5	General construction binding, wire mesh
15	1.829	2.627	23.4	7.09	20.6	Binding wire, light structural work
16	1.626	2.076	18.5	5.61	16.3	Most common construction binding gauge in India � rebar tying
17	1.422	1.588	14.1	4.29	12.5	Light construction, pre-cast binding
18	1.219	1.167	10.4	3.15	9.16	Most common motor winding gauge � also craft wire, light binding
19	1.016	0.8107	7.21	2.19	6.36	Small motor winding, instrument transformers
20	0.914	0.6567	5.84	1.77	5.16	Transformer winding, small motors, coils
21	0.813	0.5192	4.62	1.40	4.08	Fine winding, signal transformers
22	0.711	0.3970	3.53	1.07	3.12	Small motor winding, jewellery wire, craft
23	0.610	0.2923	2.60	0.789	2.29	Fuse wire, instrument coils, fine mesh
24	0.559	0.2454	2.18	0.663	1.93	Craft wire, anodised aluminium, fine winding
25	0.508	0.2027	1.80	0.547	1.59	Florist wire, tea tag wire, fine binding
26	0.457	0.1640	1.46	0.443	1.29	Fan winding, fine magnet wire, small coils
27	0.417	0.1366	1.21	0.369	1.07	Very fine instrument winding
28	0.376	0.1110	0.987	0.300	0.871	Instrument transformers, fine wire coils
29	0.345	0.09352	0.831	0.253	0.734	Fine winding, relay coils, miniature motors
30	0.315	0.07794	0.693	0.210	0.612	Miniature coils, electronic components
31	0.295	0.06835	0.608	0.185	0.537	Fine wire for relays, small solenoids
32	0.274	0.05897	0.524	0.159	0.463	Miniature motor winding, fine electronics
33	0.254	0.05067	0.450	0.137	0.398	Very fine instrument wire
34	0.234	0.04301	0.382	0.116	0.338	Micro-motors, fine solenoid wire
35	0.213	0.03564	0.317	0.0962	0.280	Micro-electronics, fine coil winding
36	0.193	0.02926	0.260	0.0790	0.230	Miniature transformers, fine gauge limit
37	0.173	0.02351	0.209	0.0635	0.185	Micro-coils, specialty instruments
38	0.152	0.01815	0.161	0.0490	0.142	Micro-instruments, hearing aid coils
39	0.132	0.01368	0.122	0.0369	0.107	Ultra-fine winding, specialist electronics
40	0.122	0.01169	0.104	0.0316	0.0918	Finest standard SWG � specialist micro-wire

* Weight per km calculated using standard material densities: Copper (ETP) 8.89 g/cm�, Aluminium (EC) 2.70 g/cm�, GI/Steel 7.85 g/cm�. Actual values may vary slightly by temper and alloy. SWG diameters per BS 3737. Use our Wire Weight Calculator for custom length and material calculations.

How SWG Sizing Works

SWG (Standard Wire Gauge), also known as Imperial Wire Gauge or British Standard Gauge (BS 3737), follows a geometric progression established in the 19th century. SWG 0 (zero) = 8.229 mm diameter. SWG 36 = 0.193 mm. Each gauge step changes the diameter by approximately 9�11%, though the exact step varies across the range � unlike AWG which uses a consistent ratio of 1.12293 per step.

In India, SWG is the standard referenced by IS (Indian Standards) specifications in electrical and construction applications. IS 280 (HB wire), IS 4826 (GI wire), IS 8130 (bare conductors), and IS 13730 (winding wire) all use SWG. If an Indian standard specifies a gauge number, that number is SWG unless otherwise stated.

Three reference points to memorise: SWG 16 = 1.63 mm (most common construction binding gauge), SWG 18 = 1.22 mm (most common motor winding gauge), SWG 10 = 3.25 mm (most common earthing conductor gauge). With these three in mind, you can estimate any other gauge by working up or down the SWG table.

SWG vs AWG: Know the Difference

The most common mistake in wire specification is confusing SWG with AWG (American Wire Gauge). The two systems use different diameter progressions. SWG 16 = 1.63 mm, while AWG 16 = 1.29 mm � a 0.34 mm difference. For electrical applications, this difference in diameter translates to a significant difference in cross-sectional area and current-carrying capacity.

Always confirm which gauge system is being used when ordering wire internationally. When in doubt, specify the diameter in millimetres � millimetres are unambiguous across all systems. Use our SWG ? AWG ? mm Converter to switch between systems instantly.

Common Uses by SWG Gauge

SWG 2�6

7.01�4.88 mm

Heavy earthing conductors
ACSR steel core wire
Substation earth grids
Gabion basket lacing
Overhead ground wire
Heavy structural binding

SWG 8�14

4.06�2.03 mm

Chain-link fencing
Transformer winding (large)
Main earthing conductors
General construction binding
Wire mesh manufacture
Bus bar links

SWG 16�20

1.63�0.91 mm

Rebar tying (SWG 16 � most common)
Motor winding (SWG 18)
Transformer winding
Craft and jewellery wire
Light binding and fabrication
Precast concrete binding

SWG 22�28

0.71�0.38 mm

Fan motor winding
Instrument transformers
Jewellery making
Anodised craft wire
Fine magnet wire
Solenoid and relay coils

SWG 30�40

0.32�0.12 mm

Miniature coil winding
Micro-motors
Hearing aid coils
Electronic components
Fine instrument wire
Specialist micro-wire

How to Use This Table When Ordering Wire

Always specify the gauge system. Say "SWG 16" or "1.63 mm" � never just "16 gauge."
Use mm for cross-reference. If you have a drawing in mm, find the closest SWG gauge from the table above and specify both on your purchase order.
Check the IS standard. Indian standards reference SWG. If your spec says IS 280 or IS 4826, the gauge in that document is SWG.
Use the weight column for cost estimation. The kg/km values in the table help you estimate coil weight and freight cost before ordering.
When in doubt, send us the mm. We can confirm the nearest SWG gauge and supply the correct material.

Need wire in a specific gauge? We supply across the full SWG 40 to SWG 0 range in aluminium, copper, GI, HB and stainless steel. Contact us with your gauge and quantity � we will confirm pricing and availability within 24 hours.

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