Gauge to mm chart for sheet, wire and tube.
Convert Standard Wire Gauge (SWG) and Birmingham Wire Gauge (BWG) to millimetres and inches. Gauge numbers are still used for sheets, wires and tube walls in India and the UK; the full chart is below.
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Full gauge table
SWG (British Standard Wire Gauge, BS 3737) is used for sheet and wire; BWG (Birmingham Wire Gauge) for tube walls. Weights are for 1 m² of steel sheet at 7.85 g/cm³.
Paste the chemistry from a mill test certificate. The checker tests it against every grade and shows which ones it meets, nearly meets or misses, element by element.
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CEV (IIW) = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Pcm = C + Si/30 + (Mn+Cu+Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B.
Limits are heat (ladle) analysis in wt%, from the first standard listed for each grade; where limits change with thickness, the thinnest bracket is used. This is a screening aid, not a certificate of conformity. Final acceptance depends on the standard edition, product analysis tolerances, mechanical tests and the purchase order.
Theoretical weight from nominal size and density. Actual weight varies within mill tolerances.
Pressure figures are inherited equation estimates, not certified ratings, hydrotest instructions or engineering approval. Confirm allowable stress, temperature, fabrication factors, corrosion and the governing code with a qualified engineer.
Pressure estimate screening only · straight-pipe equation assumptions
S is filled with the B31.3 allowable at ≤38 °C (100 °F): the lesser of UTS/3 and ⅔ of yield. For higher temperatures, type the code allowable at your design temperature. Both results below use the minimum wall (nominal minus mill tolerance minus corrosion allowance).
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5S, 10S, 40S and 80S per ASME B36.19M (stainless). Sch 10, 20, 40, 80, 160, STD, XS and XXS per ASME B36.10M (carbon and alloy). Up to 10", 40S = STD = Sch 40 and 80S = XS = Sch 80. Weights are theoretical.
Pressure ratings are an engineering estimate, not a design approval. B31.3 MAWP = 2·S·E·W·t ÷ (D − 2·Y·t), with W = 1.0 and Y = 0.4 (valid for t < D/6 and below the creep range). Barlow = 2·Sy·t ÷ D ÷ safety factor, a quick yield-based check. Flanges, fittings, valves and branch connections often rate lower than the pipe. Have the piping design checked by the responsible engineer.
Full table
Full table, all sizes
Center-to-end and length dimensions per ASME B16.9. Wall thickness and bevel match the pipe schedule ordered. Weights are published approximate weights for carbon steel, STD and XS walls. Stainless butt-weld fittings to MSS SP-43 (5S/10S) are lighter.
| Class | Ends | Matching pipe | Sizes |
|---|---|---|---|
| 2000 | Threaded only | Sch 40 / STD | ⅛" to 4" |
| 3000 | Socket weld and threaded | Sch 80 / XS | ⅛" to 4" |
| 6000 | Socket weld and threaded | Sch 160 | ⅛" to 2" (threaded to 4") |
| 9000 | Socket weld only | XXS | ½" to 2" |
Match the fitting class to the pipe schedule: a Class 3000 fitting on Sch 160 pipe is the weak point of the line. Threads are NPT (ASME B1.20.1) unless BSP is ordered. Unions are to MSS SP-83, swage nipples to MSS SP-95, branch outlets (weldolet, sockolet, threadolet) to MSS SP-97. Detailed B16.11 dimensions are being added after independent checking.
Length
Weight
Pressure / stress
Temperature
Hardness and tensile strength (approximate, carbon and alloy steel)
Type any one value. Hardness scales per ASTM E140 Table 1; approximate tensile strength per ASTM A370 Table 3 / SAE J417, for carbon and alloy steels in the annealed, normalised or quenched-and-tempered condition. Not valid for austenitic stainless, cold-worked material or non-ferrous metals. Expect ±10% on tensile.
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Aluminium tempers (what the letters mean)
- F
- As fabricated, no property guarantee
- O
- Fully annealed, softest and most formable
- H1x
- Strain hardened only (H12 quarter hard, H14 half hard, H16 three-quarter hard, H18 full hard)
- H2x
- Strain hardened, then partially annealed (H22, H24, H26)
- H3x
- Strain hardened and stabilised, used for 5xxx alloys (H32, H34, H38)
- H111 / H116 / H321
- 5xxx marine tempers; H116 and H321 are tested for exfoliation corrosion
- T3
- Solution treated, cold worked, naturally aged (2024-T3)
- T4
- Solution treated and naturally aged
- T5
- Cooled from extrusion and artificially aged (6063-T5)
- T6
- Solution treated and artificially aged: peak strength (6061-T6, 7075-T6)
- Tx51 / Tx511
- Stress relieved by stretching (T651 plate, T6511 extrusions): stable when machined
- T73 / T7351 / T76
- Over-aged for stress-corrosion resistance (7075-T7351)
- T8
- Solution treated, cold worked, artificially aged
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SWG and BWG gauge to mm and inch chart
| Gauge | SWG mm | SWG inch | BWG mm | BWG inch |
|---|---|---|---|---|
| 1 | 7.620 | 0.3000 | 7.620 | 0.3000 |
| 2 | 7.010 | 0.2760 | 7.214 | 0.2840 |
| 3 | 6.401 | 0.2520 | 6.579 | 0.2590 |
| 4 | 5.893 | 0.2320 | 6.045 | 0.2380 |
| 5 | 5.385 | 0.2120 | 5.588 | 0.2200 |
| 6 | 4.877 | 0.1920 | 5.156 | 0.2030 |
| 7 | 4.470 | 0.1760 | 4.572 | 0.1800 |
| 8 | 4.064 | 0.1600 | 4.191 | 0.1650 |
| 9 | 3.658 | 0.1440 | 3.759 | 0.1480 |
| 10 | 3.251 | 0.1280 | 3.404 | 0.1340 |
| 11 | 2.946 | 0.1160 | 3.048 | 0.1200 |
| 12 | 2.642 | 0.1040 | 2.769 | 0.1090 |
| 13 | 2.337 | 0.0920 | 2.413 | 0.0950 |
| 14 | 2.032 | 0.0800 | 2.108 | 0.0830 |
| 15 | 1.829 | 0.0720 | 1.829 | 0.0720 |
| 16 | 1.626 | 0.0640 | 1.651 | 0.0650 |
| 17 | 1.422 | 0.0560 | 1.473 | 0.0580 |
| 18 | 1.219 | 0.0480 | 1.245 | 0.0490 |
| 19 | 1.016 | 0.0400 | 1.067 | 0.0420 |
| 20 | 0.914 | 0.0360 | 0.889 | 0.0350 |
| 21 | 0.813 | 0.0320 | 0.813 | 0.0320 |
| 22 | 0.711 | 0.0280 | 0.711 | 0.0280 |
| 23 | 0.610 | 0.0240 | 0.635 | 0.0250 |
| 24 | 0.559 | 0.0220 | 0.559 | 0.0220 |
| 25 | 0.508 | 0.0200 | 0.508 | 0.0200 |
| 26 | 0.457 | 0.0180 | 0.457 | 0.0180 |
| 27 | 0.417 | 0.0164 | 0.406 | 0.0160 |
| 28 | 0.376 | 0.0148 | 0.356 | 0.0140 |
| 29 | 0.345 | 0.0136 | 0.330 | 0.0130 |
| 30 | 0.315 | 0.0124 | 0.305 | 0.0120 |
Frequently asked questions
What is 16 gauge in mm?
16 SWG is 1.626 mm (0.064 inch) and 16 BWG is 1.651 mm. Sheet gauges can differ by country and material, so confirm the thickness in mm on your order.
What is the difference between SWG and BWG?
SWG (British Standard Wire Gauge) and BWG (Birmingham Wire Gauge) are two separate gauge systems with slightly different thicknesses for the same number. BWG is often used for tube walls.
Does a higher gauge number mean thicker metal?
No. A higher gauge number means thinner metal: 10 SWG is 3.251 mm, 20 SWG is 0.914 mm.