Conversion charts
Round bar size conversion
Imperial to metric equivalents for round bar diameters, 1/32" to 20".
| Imperial (inches) | Exact metric (mm) | Nominal metric (mm) |
|---|---|---|
| 1/32" | 0.794 | 0.8 |
| 1/16" | 1.588 | 1.5 |
| 3/32" | 2.381 | 2.5 |
| 1/8" | 3.175 | 3 |
| 5/32" | 3.969 | 4 |
| 3/16" | 4.763 | 5 |
| 7/32" | 5.556 | 5.5 |
| 1/4" | 6.350 | 6 |
| 9/32" | 7.144 | 7 |
| 5/16" | 7.938 | 8 |
| 11/32" | 8.731 | 9 |
| 3/8" | 9.525 | 10 |
| 13/32" | 10.319 | 10 |
| 7/16" | 11.113 | 11 |
| 15/32" | 11.906 | 12 |
| 1/2" | 12.700 | 12 |
| 9/16" | 14.288 | 14 |
| 5/8" | 15.875 | 16 |
| 11/16" | 17.463 | 17 |
| 3/4" | 19.050 | 20 |
| 13/16" | 20.638 | 21 |
| 7/8" | 22.225 | 22 |
| 15/16" | 23.813 | 24 |
| 1" | 25.400 | 25 |
| 1 1/8" | 28.575 | 28 |
| 1 1/4" | 31.750 | 32 |
| 1 3/8" | 34.925 | 35 |
| 1 1/2" | 38.100 | 38 |
| 1 5/8" | 41.275 | 42 |
| 1 3/4" | 44.450 | 45 |
| 1 7/8" | 47.625 | 48 |
| 2" | 50.800 | 50 |
| 2 1/8" | 53.975 | 55 |
| 2 1/4" | 57.150 | 55 |
| 2 3/8" | 60.325 | 60 |
| 2 1/2" | 63.500 | 65 |
| 2 5/8" | 66.675 | 65 |
| 2 3/4" | 69.850 | 70 |
| 2 7/8" | 73.025 | 75 |
| 3" | 76.200 | 75 |
| 3 1/8" | 79.375 | 80 |
| 3 1/4" | 82.550 | 85 |
| 3 3/8" | 85.725 | 85 |
| 3 1/2" | 88.900 | 90 |
| 3 5/8" | 92.075 | 90 |
| 3 3/4" | 95.250 | 95 |
| 3 7/8" | 98.425 | 100 |
| 4" | 101.600 | 100 |
| 4 1/4" | 107.950 | 110 |
| 4 1/2" | 114.300 | 115 |
| 4 3/4" | 120.650 | 120 |
| 5" | 127.000 | 125 |
| 5 1/4" | 133.350 | 130 |
| 5 1/2" | 139.700 | 140 |
| 5 3/4" | 146.050 | 150 |
| 6" | 152.400 | 150 |
| 6 1/4" | 158.750 | 160 |
| 6 1/2" | 165.100 | 170 |
| 6 3/4" | 171.450 | 170 |
| 7" | 177.800 | 180 |
| 7 1/4" | 184.150 | 180 |
| 7 1/2" | 190.500 | 190 |
| 7 3/4" | 196.850 | 200 |
| 8" | 203.200 | 200 |
| 8 1/2" | 215.900 | 220 |
| 9" | 228.600 | 230 |
| 9 1/2" | 241.300 | 240 |
| 10" | 254.000 | 250 |
| 10 1/2" | 266.700 | 270 |
| 11" | 279.400 | 280 |
| 11 1/2" | 292.100 | 290 |
| 12" | 304.800 | 300 |
| 12 1/2" | 317.500 | 320 |
| 13" | 330.200 | 330 |
| 13 1/2" | 342.900 | 340 |
| 14" | 355.600 | 360 |
| 14 1/2" | 368.300 | 370 |
| 15" | 381.000 | 380 |
| 15 1/2" | 393.700 | 390 |
| 16" | 406.400 | 410 |
| 16 1/2" | 419.100 | 420 |
| 17" | 431.800 | 430 |
| 17 1/2" | 444.500 | 440 |
| 18" | 457.200 | 460 |
| 18 1/2" | 469.900 | 470 |
| 19" | 482.600 | 480 |
| 19 1/2" | 495.300 | 500 |
| 20" | 508.000 | 510 |
The nominal metric column shows the nearest commonly stocked metric bar size, which is usually slightly smaller than the imperial size and is not an exact equivalent. Please confirm the exact diameter and tolerance you require when placing an enquiry, and our sales team will advise on availability and the closest match.
Pipe size conversion
Nominal bore (DN / NB) to nominal pipe size (NPS) and outside diameter, 1/8" to 80".
| Nominal bore (DN/NB, mm) | Nominal bore (imperial/NPS) | Pipe outside ø (mm) |
|---|---|---|
| 6 | 1/8" | 10.2 |
| 8 | 1/4" | 13.5 |
| 10 | 3/8" | 17.2 |
| 15 | 1/2" | 21.3 |
| 20 | 3/4" | 26.9 |
| 25 | 1" | 33.7 |
| 32 | 1 1/4" | 42.4 |
| 40 | 1 1/2" | 48.3 |
| 50 | 2" | 60.3 |
| 65 | 2 1/2" | 76.1 |
| 80 | 3" | 88.9 |
| 90 | 3 1/2" | 101.6 |
| 100 | 4" | 114.3 |
| 125 | 5" | 139.7 |
| 150 | 6" | 168.3 |
| 175 | 7" | 193.7 |
| 200 | 8" | 219.1 |
| 225 | 9" | 244.5 |
| 250 | 10" | 273.0 |
| 300 | 12" | 323.9 |
| 350 | 14" | 355.6 |
| 400 | 16" | 406.4 |
| 450 | 18" | 457.0 |
| 500 | 20" | 508.0 |
| 550 | 22" | 559.0 |
| 600 | 24" | 610.0 |
| 650 | 26" | 660.0 |
| 700 | 28" | 711.0 |
| 750 | 30" | 762.0 |
| 800 | 32" | 813.0 |
| 850 | 34" | 864.0 |
| 900 | 36" | 914.0 |
| 950 | 38" | 965.0 |
| 1000 | 40" | 1016.0 |
| 1050 | 42" | 1067.0 |
| 1100 | 44" | 1118.0 |
| 1150 | 46" | 1168.0 |
| 1200 | 48" | 1219.0 |
| 1300 | 52" | 1321.0 |
| 1400 | 56" | 1422.0 |
| 1500 | 60" | 1524.0 |
| 1600 | 64" | 1626.0 |
| 1700 | 68" | 1727.0 |
| 1800 | 72" | 1829.0 |
| 1900 | 76" | 1930.0 |
| 2000 | 80" | 2032.0 |
Outside diameters shown follow the European series (EN 10220 / EN 10255 / ISO 1127). A small number of sizes differ under the American standard (ASME B36.10): 3/4" = 26.7mm, 1" = 33.4mm, 1 1/4" = 42.2mm, 2 1/2" = 73.0mm and 5" = 141.3mm. Please let us know which standard applies to your project and we will confirm the correct dimensions.
ISO 286-2 round bar tolerances
h = minus; k = plus. Values are the full tolerance band for each ISO 286-2 standard tolerance grade, IT8 to IT12.
| Nominal size, dia mm | IT8 | IT9 | IT10 | IT11 | IT12 |
|---|---|---|---|---|---|
| >10 - 18 | 0.027 (0.00106") | 0.043 (0.00169") | 0.07 (0.00276") | 0.11 (0.00433") | 0.18 (0.00709") |
| >18 - 30 | 0.033 (0.00130") | 0.052 (0.00205") | 0.084 (0.00331") | 0.13 (0.00512") | 0.21 (0.00827") |
| >30 - 50 | 0.039 (0.00154") | 0.062 (0.00244") | 0.1 (0.00394") | 0.16 (0.00630") | 0.25 (0.00984") |
| >50 - 80 | 0.046 (0.00181") | 0.074 (0.00291") | 0.12 (0.00472") | 0.19 (0.00748") | 0.3 (0.01181") |
| >80 - 120 | 0.054 (0.00213") | 0.087 (0.00343") | 0.14 (0.00551") | 0.22 (0.00866") | 0.35 (0.01378") |
| >120 - 180 | 0.063 (0.00248") | 0.1 (0.00394") | 0.16 (0.00630") | 0.25 (0.00984") | 0.4 (0.01575") |
| >180 - 250 | 0.072 (0.00283") | 0.115 (0.00453") | 0.185 (0.00728") | 0.29 (0.01142") | 0.46 (0.01811") |
| >250 - 315 | 0.081 (0.00319") | 0.13 (0.00512") | 0.21 (0.00827") | 0.32 (0.01260") | 0.52 (0.02047") |
| >315 - 400 | 0.089 (0.00350") | 0.14 (0.00551") | 0.23 (0.00906") | 0.36 (0.01417") | 0.57 (0.02244") |
Values are shown in millimetres with the inch equivalent in brackets. For an h tolerance the band is applied minus from the nominal size, and for a k tolerance it is applied plus. Please confirm the grade and nominal size you require when placing an enquiry.
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