ASTM & ISO Standard Thickness Tables – Gauge to mm | India 2026

ASTM & ISO Standard Thickness Tables – India 2026

Complete gauge-to-mm reference for ASTM (US Standard Gauge), British SWG, ISO preferred series and IS (BIS) standards — steel, aluminium and stainless sheets for Indian fabricators and engineers.

ASTM / SWG / IS / ISO Steel, Al & SS Gauge ↔ mm ↔ inch Mobile Friendly IS / BIS India

ASTM & ISO Gauge to mm Converter

Select your gauge standard, enter a gauge number and instantly get thickness in mm and inches

Gauge Number (ASTM / USG)

Thickness (ISO / IS)

Material

Thickness

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Thickness

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inches

Weight (kg/m²)

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kg/m²

Standard

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reference

How to Use the ASTM & ISO Thickness Reference

Three simple ways to find the standard thickness you need

Choose Your Standard

Select ASTM / US Gauge if your drawing or supplier uses gauge numbers per ASTM A480/A568. Choose SWG (Standard Wire Gauge) — the most common gauge system in India. Use ISO / IS Metric for metric mm-based specifications per IS 1730 or IS 737.

Enter Gauge or Thickness

For ASTM and SWG modes, type the gauge number and the converter instantly shows mm and inch equivalents. For ISO mode, enter a thickness in mm to see the nearest standard ISO R10 value and IS equivalent.

Select Material

Different gauge standards apply to different materials. ASTM USG applies to carbon and stainless steel. SWG is widely used for all metals in India. kg/m² result adjusts automatically based on the material density selected.

Cross-Check Tables Below

Use the full reference tables below for complete gauge series. The ASTM A568 table covers US carbon steel gauges, the SWG table covers all metals used in India, and the IS 1730 table covers BIS standard plate thicknesses.

Verify with Mill Certificate

Always confirm the thickness and tolerance from the mill test certificate. ASTM A568 allows ±0.005–0.010" tolerance; IS 1730 allows ±0.25 mm for sheets under 4 mm and ±6.25% for plates.

Use for Procurement

When ordering from Indian distributors who quote in SWG, use the SWG↔mm table to convert to IS/ISO metric for formal drawings, BOQ submissions, and CPWD/PWD tender documents.

ASTM Standard Thickness Table – Carbon Steel (US Gauge)

ASTM A568 / US Standard Gauge (USG) for carbon and structural steel sheet — gauge number to mm and inches

ASTM A568 ASTM A1008 Carbon / MS Steel Density: 7.85 g/cm³

Gauge (USG)	Thickness (inches)	Thickness (mm)	Weight (kg/m²)	IS 1730 Nearest (mm)
3 ga	0.2391"	6.07	47.67	6.0
4 ga	0.2242"	5.69	44.72	5.0 / 6.0
5 ga	0.2092"	5.31	41.71	5.0
6 ga	0.1943"	4.93	38.73	5.0
7 ga	0.1793"	4.55	35.75	4.0 / 5.0
8 ga	0.1644"	4.18	32.81	4.0
9 ga	0.1495"	3.80	29.83	4.0
10 ga	0.1345"	3.42	26.85	3.15
11 ga	0.1196"	3.04	23.86	3.0
12 ga	0.1046"	2.66	20.88	2.5
13 ga	0.0897"	2.28	17.90	2.0 / 2.5
14 ga	0.0747"	1.90	14.91	2.0
15 ga	0.0673"	1.71	13.43	1.6
16 ga	0.0598"	1.52	11.93	1.6
17 ga	0.0538"	1.37	10.75	1.25
18 ga	0.0478"	1.21	9.53	1.2
19 ga	0.0418"	1.06	8.33	1.0
20 ga	0.0359"	0.91	7.15	0.9 / 1.0
22 ga	0.0299"	0.76	5.97	0.8
24 ga	0.0239"	0.61	4.77	0.6
26 ga	0.0179"	0.45	3.56	0.5
28 ga	0.0149"	0.38	2.97	0.4
30 ga	0.0120"	0.30	2.39	0.3

* Weight kg/m² calculated at carbon steel density 7.85 g/cm³. Thickness values per ASTM A568/A568M. IS 1730 nearest is the closest BIS standard thickness per Bureau of Indian Standards.

SWG Standard Thickness Table – All Metals (India)

Standard Wire Gauge (SWG / BS 3737) — the most widely used gauge system in India for steel, aluminium, copper and GI sheets

SWG / BS 3737 Common in India Steel, Al, Cu, GI mm & inches

SWG	Thickness (mm)	Thickness (inches)	Steel kg/m²	Al kg/m²	GI kg/m²
1 SWG	7.620	0.300"	59.82	20.57	60.80
2 SWG	7.010	0.276"	55.03	18.93	55.93
3 SWG	6.401	0.252"	50.25	17.28	51.07
4 SWG	5.893	0.232"	46.26	15.91	47.02
5 SWG	5.385	0.212"	42.27	14.54	42.97
6 SWG	4.877	0.192"	38.28	13.17	38.92
7 SWG	4.470	0.176"	35.09	12.07	35.67
8 SWG	4.064	0.160"	31.90	10.97	32.43
9 SWG	3.658	0.144"	28.72	9.88	29.19
10 SWG	3.251	0.128"	25.52	8.78	25.94
11 SWG	2.946	0.116"	23.13	7.95	23.51
12 SWG	2.642	0.104"	20.74	7.13	21.08
13 SWG	2.337	0.092"	18.35	6.31	18.65
14 SWG	2.032	0.080"	15.95	5.49	16.22
15 SWG	1.829	0.072"	14.36	4.94	14.60
16 SWG	1.626	0.064"	12.76	4.39	12.97
17 SWG	1.422	0.056"	11.16	3.84	11.35
18 SWG	1.219	0.048"	9.57	3.29	9.73
19 SWG	1.016	0.040"	7.98	2.74	8.11
20 SWG	0.914	0.036"	7.17	2.47	7.29
21 SWG	0.813	0.032"	6.38	2.20	6.49
22 SWG	0.711	0.028"	5.58	1.92	5.67
23 SWG	0.610	0.024"	4.79	1.65	4.87
24 SWG	0.559	0.022"	4.39	1.51	4.46
25 SWG	0.508	0.020"	3.99	1.37	4.06
26 SWG	0.457	0.018"	3.59	1.23	3.65
27 SWG	0.417	0.0164"	3.27	1.13	3.33
28 SWG	0.376	0.0148"	2.95	1.02	3.00
29 SWG	0.345	0.0136"	2.71	0.93	2.75
30 SWG	0.315	0.0124"	2.47	0.85	2.51

* SWG values per BS 3737. Steel kg/m² at 7.85 g/cm³; Aluminium at 2.70 g/cm³; GI (Galvanised) at 7.95 g/cm³ including zinc coating. SWG is the predominant gauge system used by Indian steel stockists and fabricators. See also our Gauge to mm Converter for quick lookups.

ASTM A480 Thickness Table – Stainless Steel Sheet

ASTM A480 / US Gauge for stainless steel flat-rolled products — grades 304, 316, 410, 430

ASTM A480 Stainless Steel 304 / 316 / 410 / 430 Density: 7.93 g/cm³

Gauge (USG)	Thickness (inches)	Thickness (mm)	SS 304 kg/m²	SS 316 kg/m²	IS 6911 Nearest (mm)
7 ga	0.1875"	4.763	37.77	38.01	5.0
8 ga	0.1719"	4.369	34.61	34.83	4.0
9 ga	0.1563"	3.969	31.45	31.67	4.0
10 ga	0.1406"	3.571	28.31	28.50	3.5
11 ga	0.1250"	3.175	25.18	25.34	3.0
12 ga	0.1094"	2.779	22.04	22.19	3.0
13 ga	0.0938"	2.381	18.88	19.01	2.5
14 ga	0.0781"	1.984	15.73	15.84	2.0
15 ga	0.0703"	1.786	14.16	14.26	2.0
16 ga	0.0625"	1.588	12.59	12.68	1.6
17 ga	0.0563"	1.429	11.33	11.41	1.5
18 ga	0.0500"	1.270	10.07	10.14	1.25
19 ga	0.0438"	1.113	8.82	8.88	1.0
20 ga	0.0375"	0.953	7.55	7.60	1.0
22 ga	0.0313"	0.794	6.30	6.34	0.8
24 ga	0.0250"	0.635	5.03	5.07	0.6
26 ga	0.0188"	0.477	3.78	3.81	0.5
28 ga	0.0156"	0.396	3.14	3.16	0.4

* Stainless steel gauge uses 1/16" increments (different from carbon steel USG). SS 304 density = 7.93 g/cm³; SS 316 density = 7.98 g/cm³ per ASTM A480/A480M. IS 6911 is the BIS equivalent for stainless steel sheets.

IS 1730 & ISO Standard Thickness Table – India

BIS IS 1730 preferred thicknesses for steel plates and sheets — the metric standard used in Indian engineering drawings, BOQs and tender specifications

IS 1730 (BIS) ISO 9445 ISO 3574 Metric mm India Standard

IS 1730 Thickness (mm)	ISO Preferred (mm)	MS Steel kg/m²	SS 304 kg/m²	Al 6061 kg/m²	Nearest SWG	Nearest USG
0.50	0.50	3.93	3.97	1.35	25 SWG	–
0.63	0.63	4.95	4.98	1.70	23–24 SWG	–
0.80	0.80	6.28	6.34	2.16	21–22 SWG	–
1.00	1.00	7.85	7.93	2.70	19–20 SWG	–
1.20	1.25	9.42	9.52	3.24	18 SWG	18 ga
1.60	1.60	12.56	12.69	4.32	16 SWG	16 ga
2.00	2.00	15.70	15.86	5.40	14 SWG	14 ga
2.50	2.50	19.63	19.83	6.75	12 SWG	12–13 ga
3.00	3.15	23.55	23.79	8.10	10–11 SWG	11 ga
3.15	3.15	24.73	24.98	8.51	10 SWG	10 ga
4.00	4.00	31.40	31.72	10.80	8 SWG	8 ga
5.00	5.00	39.25	39.65	13.50	6 SWG	5–6 ga
6.00	6.30	47.10	47.58	16.20	4–5 SWG	3–4 ga
8.00	8.00	62.80	63.44	21.60	2 SWG	–
10.00	10.00	78.50	79.30	27.00	–	–
12.00	12.50	94.20	95.16	32.40	–	–
14.00	–	109.90	111.02	37.80	–	–
16.00	16.00	125.60	126.88	43.20	–	–
20.00	20.00	157.00	158.60	54.00	–	–
25.00	25.00	196.25	198.25	67.50	–	–
28.00	–	219.80	221.84	75.60	–	–
32.00	31.50	251.20	253.76	86.40	–	–
36.00	–	282.60	285.48	97.20	–	–
40.00	40.00	314.00	317.20	108.00	–	–
50.00	50.00	392.50	396.50	135.00	–	–

* IS 1730:1989 covers flat products of steel — plates, sheets and strips. ISO 9445 governs cold-rolled stainless. ISO 3574 governs cold-reduced carbon steel. Nearest SWG/USG values are approximate — always specify actual mm thickness on engineering drawings per IS 1730. Al kg/m² at 2.70 g/cm³.

ASTM B209 Thickness Table – Aluminium Sheet & Plate

ASTM B209 standard thicknesses for aluminium alloy sheet and plate — commonly referenced in India for aerospace and industrial aluminium procurement

ASTM B209 Aluminium Sheet & Plate IS 737 Equivalent Density: 2.70 g/cm³

Thickness (inches)	Thickness (mm)	Category	6061 kg/m²	7075 kg/m²	IS 737 Nearest (mm)
0.016"	0.41	Sheet	1.10	1.15	0.4
0.020"	0.51	Sheet	1.37	1.43	0.5
0.025"	0.64	Sheet	1.72	1.79	0.63
0.032"	0.81	Sheet	2.20	2.29	0.8
0.040"	1.02	Sheet	2.74	2.86	1.0
0.050"	1.27	Sheet	3.43	3.57	1.25
0.063"	1.60	Sheet	4.32	4.50	1.6
0.080"	2.03	Sheet	5.49	5.71	2.0
0.090"	2.29	Sheet	6.17	6.43	2.0 / 2.5
0.100"	2.54	Sheet	6.86	7.14	2.5
0.125"	3.18	Sheet	8.57	8.93	3.0
0.160"	4.06	Sheet	10.97	11.41	4.0
0.190"	4.83	Sheet/Plate	13.03	13.57	5.0
0.250"	6.35	Plate	17.14	17.84	6.0
0.313"	7.95	Plate	21.46	22.34	8.0
0.375"	9.53	Plate	25.71	26.77	10.0
0.500"	12.70	Plate	34.29	35.69	12.0
0.625"	15.88	Plate	42.86	44.62	16.0
0.750"	19.05	Plate	51.43	53.54	20.0
1.000"	25.40	Plate	68.58	71.39	25.0

* Thickness values per ASTM B209/B209M. IS 737:2019 is the BIS equivalent for Indian procurement. 6061 density = 2.70 g/cm³; 7075 density = 2.81 g/cm³. Sheet = up to 6.35 mm; Plate = above 6.35 mm per ASTM classification.

ASTM & ISO Thickness Standards – Overview

Key standards referenced in India for sheet and plate metal thickness specifications

ASTM A568 / A568M

USG Steel

Carbon & HSLA Sheet

General requirements for carbon, structural and HSLA steel flat-rolled products. Defines US Standard Gauge for steel sheet and strip.

ASTM A480 / A480M

SS Gauge

Stainless Steel Sheet

Covers flat-rolled stainless and heat-resisting steel plate, sheet and strip. Uses 1/16" gauge increments different from carbon steel USG.

ASTM B209 / B209M

Al Sheet

Aluminium Alloy

Aluminium alloy sheet and plate in inches. Covers alloys 1100, 2024, 3003, 5052, 6061, 7075 and others.

BS 3737 / SWG

SWG India

All Metals

Standard Wire Gauge — British standard widely adopted across India. Used by stockists for steel, aluminium, copper and GI sheets.

IS 1730 (BIS)

IS Metric

Steel Plate & Sheet

Bureau of Indian Standards specification for dimensions and tolerances of steel flat products. Mandatory reference for CPWD, PWD, railway and defence procurement.

IS 737 (BIS)

IS Al

Aluminium Sheet

BIS standard for wrought aluminium and aluminium alloy sheet and strip for general engineering purposes. 2019 revision aligns with ISO 6361.

ISO 9445

ISO SS

Stainless Steel

ISO standard for continuously cold-rolled stainless steel narrow strip, wide strip, plate/sheet and cut lengths. Thickness tolerances per IS 6911 for India.

ISO 3574

ISO Carbon

Cold-Reduced Steel

ISO standard for cold-reduced carbon steel sheet of commercial and drawing quality. IS 513 is the direct BIS equivalent used in Indian automotive and appliance industries.

IS 6911 (BIS)

IS SS

Stainless Steel Sheet

BIS specification for stainless steel plates, sheets and strips. Covers grades 304, 304L, 316, 316L, 410, 430 with IS-specific thickness tolerances.

Why ASTM & ISO Thickness Standards Matter in India

Real-world applications where correct standard thickness selection is critical for Indian engineers

Tendering & BOQ

Government tenders (CPWD, MES, Indian Railways) specify steel by IS 1730 metric mm. Converting a supplier's SWG quote to the IS thickness is essential for correct BOQ preparation and rate approval.

Drawing Specifications

Engineering drawings for export orders may specify ASTM gauge while Indian fabricators work in SWG. Correct conversion avoids costly production errors and material rejections during quality inspection.

Aerospace & Defence

HAL, DRDO and private aerospace firms must cross-reference ASTM B209 (inch-based) with IS 737 (mm-based) when sourcing aluminium sheet for airframe components and structural assemblies.

Automotive Industry

OEM automotive specifications in India typically use ISO/IS metric mm but supplier mill certificates often reference ASTM A568 USG. Thickness cross-referencing is a daily activity for procurement teams.

Fabrication Shops

Sheet metal fabricators across India receive job orders in mixed standards. Converting between SWG, USG, and IS mm instantly — without calculation errors — improves throughput and reduces material waste.

Quality & Inspection

Third-party inspectors (TPI) for steel imports verify thickness against ASTM or ISO standards. Knowing the allowable thickness tolerance per standard is required to accept or reject incoming material batches.

Pro Tips – Using Thickness Standards in India

Practical guidance from experienced Indian fabricators and engineers

SWG ≠ USG — Never Confuse Them

16 SWG = 1.626 mm but 16 USG (carbon steel) = 1.519 mm — a difference of over 0.1 mm. On thin-gauge pressings this difference can cause fit-up and weld gap problems. Always confirm which gauge system your supplier is quoting.

Specify mm on All Indian Drawings

IS 1730 and BIS standards require thickness to be specified in mm on engineering drawings. Never use gauge numbers alone on formal drawings for CPWD, PWD, or IS-certified work — always state the mm equivalent.

Understand Thickness Tolerances

ASTM A568 allows −0 to +0.010" on most thicknesses. IS 1730 allows ±0.25 mm for sheets up to 3 mm. These tolerances mean a "2 mm" sheet could be 1.75–2.25 mm. Use the upper tolerance in weight and cost calculations.

IS 513 vs IS 1079 — Know the Difference

IS 513 covers cold-rolled (CR) carbon steel sheets for drawing and forming. IS 1079 covers hot-rolled (HR) sheets. CR sheets have tighter thickness tolerances and better surface finish — specify correctly to avoid wrong material supply.

ASTM vs IS — Material Equivalence

ASTM A36 ≈ IS 2062 E250, ASTM A240 Gr 304 ≈ IS 6911 Gr 04Cr18Ni10. These are not exact equivalents — chemical composition limits and testing requirements differ. For critical applications, always review both standards and seek a dual-certified mill certificate. See also our MS Sheet Weight page for IS 2062 grades.

Use kg/m² for Price Verification

Indian steel is priced per kg (₹/kg). Multiply the kg/m² from the table by your sheet area in m² to get the theoretical weight. Compare against the supplier's invoice weight — a variance of more than 5% should be queried with the mill certificate.

Related Calculators & Reference Pages

More weight calculators and reference tools for Indian fabricators and engineers

Frequently Asked Questions – ASTM & ISO Thickness Standards

Common questions from Indian engineers, fabricators and procurement teams

What is the difference between ASTM, ISO and IS thickness standards?

ASTM (American Society for Testing and Materials) standards define thickness in inches using gauge numbers — primarily used in the USA and referenced in Indian import specifications. ISO standards (International Organization for Standardization) use metric mm values in preferred number series (R10/R20). IS (BIS) standards from the Bureau of Indian Standards are India's national standards — IS 1730 (steel), IS 737 (aluminium), IS 6911 (stainless) — and are mandatory for government procurement in India.

What is SWG and why is it used in India?

SWG (Standard Wire Gauge, also called British Standard Wire Gauge, BS 3737) is a UK-origin gauge system where higher numbers indicate thinner material. It is widely used in India because of historical British engineering influence. Most Indian steel and aluminium stockists, sheet metal fabricators, and hardware traders quote thickness in SWG rather than mm. Common sizes — 16 SWG (1.626 mm), 18 SWG (1.219 mm), 20 SWG (0.914 mm) — are well understood by Indian tradespeople. However, IS 1730 requires formal drawings to specify thickness in mm.

What is 16 gauge sheet thickness in mm for steel?

It depends on which gauge system is being used:

16 SWG (most common in India) = 1.626 mm
16 USG / ASTM A568 (carbon steel) = 1.519 mm
16 USG / ASTM A480 (stainless steel) = 1.588 mm

Always confirm which system your supplier is using before placing an order. The ~0.1 mm difference between SWG and USG is significant for precision sheetmetal work.

What is the IS 1730 standard for steel plates in India?

IS 1730:1989 (reaffirmed 2019) is the Bureau of Indian Standards specification for Steel Plates, Sheets, Strips and Flats for Structural and General Engineering Purposes — Dimensions. It specifies preferred metric thicknesses from 0.5 mm to 50 mm in a series aligned with ISO preferred numbers. IS 1730 is the mandatory reference for thickness specification on engineering drawings submitted to government departments, public sector undertakings, and IS-certified fabricators across India.

Is ASTM A36 equivalent to IS 2062 steel in India?

ASTM A36 and IS 2062 Grade E250 are considered broadly equivalent in terms of yield strength (250 MPa / 36 ksi) and are commonly substituted in practice. However, they are not identical — ASTM A36 has different carbon equivalent limits, Charpy impact test requirements, and test piece orientation specifications compared to IS 2062. For critical structural applications (bridges, pressure vessels, seismic zones), always confirm equivalence with a structural engineer and obtain dual-certified mill test certificates if required.

What is the ISO preferred thickness series for sheet metal?

The ISO preferred thickness series is based on the R10 Renard number series (10 steps per decade, ratio ≈ 1.25): 1.0, 1.25, 1.6, 2.0, 2.5, 3.15, 4.0, 5.0, 6.3, 8.0, 10.0, 12.5, 16.0, 20.0, 25.0 mm. IS 1730 follows a similar metric series — 1.0, 1.2, 1.6, 2.0, 2.5, 3.0, 3.15, 4.0, 5.0, 6.0, 8.0, 10.0, 12.0, 16.0, 20.0, 25.0 mm — with some additional intermediate values. Specifying preferred thicknesses reduces tooling cost and improves material availability from Indian mills like SAIL, Tata Steel, and JSW Steel.

What does ASTM A480 say about stainless steel sheet

ASTM A480/A480M is the general requirements standard for flat-rolled stainless and heat-resisting steel plate, sheet and strip. Key points relevant to Indian procurement:

Stainless gauge uses 1/16" increments — different from carbon steel USG
Thickness tolerance varies by width and thickness — typically ±0.005" to ±0.010"
Covers grades 304, 304L, 316, 316L, 321, 410, 430 and many others
Indian equivalent is IS 6911 from BIS for stainless sheet and plate

When importing stainless sheet from Europe or USA, the mill certificate will reference A480. Indian buyers should cross-reference with IS 6911 tolerances before acceptance.

What is the nearest IS 1730 thickness to 16 SWG and 18 SWG?

16 SWG = 1.626 mm → Nearest IS 1730 = 1.6 mm (difference: +0.026 mm)
18 SWG = 1.219 mm → Nearest IS 1730 = 1.2 mm (difference: +0.019 mm)
20 SWG = 0.914 mm → Nearest IS 1730 = 0.9 mm or 1.0 mm
14 SWG = 2.032 mm → Nearest IS 1730 = 2.0 mm (difference: +0.032 mm)

For procurement, the SWG thickness is always slightly above the IS nominal — meaning an SWG sheet is marginally heavier than its IS equivalent. This difference is within IS 1730 tolerance for most grades and is generally accepted by quality inspectors.

Which Indian mills supply ASTM-certified steel sheets?

Several major Indian steel producers supply dual IS/ASTM certified flat products:

Tata Steel — supplies ASTM A36, A240 SS 304/316, and IS 2062 certified sheets
JSW Steel — HR and CR sheets per IS 1079, IS 513 with ASTM cross-certificates available
SAIL (Steel Authority of India) — IS 1730, IS 2062 standard; ASTM equivalents on request
Hindalco / NALCO — IS 737 aluminium sheets; ASTM B209 cross-certification for aerospace grades
Jindal Stainless — IS 6911 stainless sheet with ASTM A240/A480 cross-certification

Always request a mill test certificate (MTC) specifying both IS and ASTM standards when dual certification is required for export or defence contracts.

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