How do you measure an O-Ring?

How do you measure an O-ring?

There are THREE crucial dimensions to measure when trying to find the right size of O Ring. 

They are

Cross Section

Outer Diameter (OD)

Inner Diameter

If you know these dimensions, the material and durometer (hardness) you need, you're all set!

So let's go through them all, and figure out how to measure your current O-Ring to get a replacement, or how to measure your machine, if you don't have an old O-Ring to go off of.

CROSS SECTION: This is the width of one side of the O-Ring. Since O-Rings are circular, this means that if you measure the height while it's lying flat on a table, that is also the cross section.  Standard size O-Rings have cross sections that come in 1/32", 1/16", 3/32", 1/8", 3/16", and 1/4", but there are special sizes in standard, and Metric sizes as well.  If you're looking at the machine but no O-Ring, this is the width of the groove that the O-Ring fits in (but be careful! Some machines were built to hold 1 or 2 Back-Up rings in addition to the O-Ring).

OUTER DIAMETER (OD):  The OD is the total width of the O-Ring, from one outside edge to the other.  If you're looking at the groove where the O-Ring sits, it might be the diameter outside of the groove (but, again, be careful, because that's not always true!)

INNER DIAMETER (ID):  The ID is the measurement of the interior of the O-Ring, from one inside wall to the opposite inside wall.  If you're looking at the groove where the O-Ring fits, it's the diameter of the groove.

COMING SOON:  We'll discuss how to decide which material you need for your O-Ring. 

If you want to find the right AS-568A Standard O-Ring Size, and you now know the three crucial dimensions, please check out our O-Ring size chart.  Or start shopping for O-Rings now!

O-ring Size Chart, AS568 O-ring Chart, AS568 O-ring Sizes

O-ring Size Chart

Welcome to our AS568 O-ring Size Chart section

This O-ring size chart provides a list of standard AS568 O-ring sizes. Most industries consider AS568 specifications, standard O-ring sizes. Each AS568 dash number is a unique number that denotes specific O-ring dimensions. If you need to know how to size an O-ring, consider starting with these AS568 O-ring sizes so you will not have to purchase custom O-ring sizes which can be more costly. This AS568 O-ring chart is a SAE size standard for O-rings and shows AS568 Rev B or AS568B O-ring sizes which supersedes AS568 Rev A or AS568A O-ring dimensions. We have millions of AS568 O-rings in stock which can be purchased easily through our O-rings Online Store.

AS568 Number Nominal Actual Nominal Actual   ID ID CS CS 001 1/32 0.029 1/32 0.040 002 3/64 0.042 3/64 0.050 003 1/16 0.056 1/16 0.060 004 5/64 0.070 1/16 0.070 005 3/32 0.101 1/16 0.070 006 1/8 0.114 1/16 0.070 007 5/32 0.145 1/16 0.070 008 3/16 0.176 1/16 0.070 009 7/32 0.208 1/16 0.070 010 1/4 0.239 1/16 0.070 011 5/16 0.301 1/16 0.070 012 3/8 0.364 1/16 0.070 013 7/16 0.426 1/16 0.070 014 1/2 0.489 1/16 0.070 015 9/16 0.551 1/16 0.070 016 5/8 0.614 1/16 0.070 017 11/16 0.676 1/16 0.070 018 3/4 0.739 1/16 0.070 019 13/16 0.801 1/16 0.070 020 7/8 0.864 1/16 0.070 021 15/16 0.926 1/16 0.070 022 1 0.989 1/16 0.070 023 1-1/16 1.051 1/16 0.070 024 1-1/8 1.114 1/16 0.070 025 1-3/16 1.176 1/16 0.070 026 1-1/4 1.239 1/16 0.070 027 1-5/16 1.301 1/16 0.070 028 1-3/8 1.364 1/16 0.070 029 1-1/2 1.489 1/16 0.070 030 1-5/8 1.614 1/16 0.070 031 1-3/4 1.739 1/16 0.070 032 1-7/8 1.864 1/16 0.070 033 2 1.989 1/16 0.070 034 2-1/8 2.114 1/16 0.070 035 2-1/4 2.239 1/16 0.070 036 2-3/8 2.364 1/16 0.070 037 2-1/2 2.489 1/16 0.070 038 2-5/8 2.614 1/16 0.070 039 2-3/4 2.739 1/16 0.070 040 2-7/8 2.864 1/16 0.070 041 3 2.989 1/16 0.070 042 3-1/4 3.239 1/16 0.070 043 3-1/2 3.489 1/16 0.070 044 3-3/4 3.739 1/16 0.070 045 4 3.989 1/16 0.070 046 4-1/4 4.239 1/16 0.070 047 4-1/2 4.489 1/16 0.070 048 4-3/4 4.739 1/16 0.070 049 5 4.989 1/16 0.070 050 5-1/4 5.239 1/16 0.070 102 1/16 0.049 3/32 0.103 103 3/32 0.081 3/32 0.103 104 1/8 0.112 3/32 0.103 105 5/32 0.143 3/32 0.103 106 3/16 0.174 3/32 0.103 107 7/32 0.206 3/32 0.103 108 1/4 0.237 3/32 0.103 109 5/16 0.299 3/32 0.103 110 3/8 0.362 3/32 0.103 111 7/16 0.424 3/32 0.103 112 1/2 0.487 3/32 0.103 113 9/16 0.549 3/32 0.103 114 5/8 0.612 3/32 0.103 115 11/16 0.674 3/32 0.103 116 3/4 0.737 3/32 0.103 117 13/16 0.799 3/32 0.103 118 7/8 0.862 3/32 0.103 119 15/16 0.924 3/32 0.103 120 1 0.987 3/32 0.103 121 1-1/16 1.049 3/32 0.103 122 1-1/8 1.112 3/32 0.103 123 1-3/16 1.174 3/32 0.103 124 1-1/4 1.237 3/32 0.103 125 1-5/16 1.299 3/32 0.103 126 1-3/8 1.362 3/32 0.103 127 1-7/16 1.424 3/32 0.103 128 1-1/2 1.487 3/32 0.103 129 1-9/16 1.549 3/32 0.103 130 1-5/8 1.612 3/32 0.103 131 1-11/16 1.674 3/32 0.103 132 1-3/4 1.737 3/32 0.103 133 1-13/16 1.799 3/32 0.103 134 1-7/8 1.862 3/32 0.103 135 1-15/16 1.925 3/32 0.103 136 2 1.987 3/32 0.103 137 2-1/16 2.050 3/32 0.103 138 2-1/8 2.112 3/32 0.103 139 2-3/16 2.175 3/32 0.103 140 2-1/4 2.237 3/32 0.103 141 2-5/16 2.300 3/32 0.103 142 2-3/8 2.362 3/32 0.103 143 2-7/16 2.425 3/32 0.103 144 2-1/2 2.487 3/32 0.103 145 2-9/16 2.550 3/32 0.103 146 2-5/8 2.612 3/32 0.103 147 2-11/16 2.675 3/32 0.103 148 2-3/4 2.737 3/32 0.103 149 2-13/16 2.800 3/32 0.103 150 2-7/8 2.862 3/32 0.103 151 3 2.987 3/32 0.103 152 3-1/4 3.237 3/32 0.103 153 3-1/2 3.487 3/32 0.103 154 3-3/4 3.737 3/32 0.103 155 4 3.987 3/32 0.103 156 4-1/4 4.237 3/32 0.103 157 4-1/2 4.487 3/32 0.103 158 4-3/4 4.737 3/32 0.103 159 5 4.987 3/32 0.103 160 5-1/4 5.237 3/32 0.103 161 5-1/2 5.487 3/32 0.103 162 5-3/4 5.737 3/32 0.103 163 6 5.987 3/32 0.103 164 6-1/4 6.237 3/32 0.103 165 6-1/2 6.487 3/32 0.103 166 6-3/4 6.737 3/32 0.103 167 7 6.987 3/32 0.103 168 7-1/4 7.237 3/32 0.103 169 7-1/2 7.487 3/32 0.103 170 7-3/4 7.737 3/32 0.103 171 8 7.987 3/32 0.103 172 8-1/4 8.237 3/32 0.103 173 8-1/2 8.487 3/32 0.103 174 8-3/4 8.737 3/32 0.103 175 9 8.987 3/32 0.103 176 9-1/4 9.237 3/32 0.103 177 9-1/2 9.487 3/32 0.103 178 9-3/4 9.737 3/32 0.103 201 3/16 0.171 1/8 0.139 202 1/4 0.234 1/8 0.139 203 5/16 0.296 1/8 0.139 204 3/8 0.359 1/8 0.139 205 7/16 0.421 1/8 0.139 206 1/2 0.484 1/8 0.139 207 9/16 0.546 1/8 0.139 208 5/8 0.609 1/8 0.139 209 11/16 0.671 1/8 0.139 210 3/4 0.734 1/8 0.139 211 13/16 0.796 1/8 0.139 212 7/8 0.859 1/8 0.139 213 15/16 0.921 1/8 0.139 214 1 0.984 1/8 0.139 215 1-1/16 1.046 1/8 0.139 216 1-1/8 1.109 1/8 0.139 217 1-3/16 1.171 1/8 0.139 218 1-1/4 1.234 1/8 0.139 219 1-5/16 1.296 1/8 0.139 220 1-3/8 1.359 1/8 0.139 221 1-7/16 1.421 1/8 0.139 222 1-1/2 1.484 1/8 0.139 223 1-5/8 1.609 1/8 0.139 224 1-3/4 1.734 1/8 0.139 225 1-7/8 1.859 1/8 0.139 226 2 1.984 1/8 0.139 227 2-1/8 2.109 1/8 0.139 228 2-1/4 2.234 1/8 0.139 229 2-3/8 2.359 1/8 0.139 230 2-1/2 2.484 1/8 0.139 231 2-5/8 2.609 1/8 0.139 232 2-3/4 2.734 1/8 0.139 233 2-7/8 2.859 1/8 0.139 234 3 2.984 1/8 0.139 235 3-1/8 3.109 1/8 0.139 236 3-1/4 3.234 1/8 0.139 237 3-3/8 3.359 1/8 0.139 238 3-1/2 3.484 1/8 0.139 239 3-5/8 3.609 1/8 0.139 240 3-3/4 3.734 1/8 0.139 241 3-7/8 3.859 1/8 0.139 242 4 3.984 1/8 0.139 243 4-1/8 4.109 1/8 0.139 244 4-1/4 4.234 1/8 0.139 245 4-3/8 4.359 1/8 0.139 246 4-1/2 4.484 1/8 0.139 247 4-5/8 4.609 1/8 0.139 248 4-3/4 4.734 1/8 0.139 249 4-7/8 4.859 1/8 0.139 250 5 4.984 1/8 0.139 251 5-1/8 5.109 1/8 0.139 252 5-1/4 5.234 1/8 0.139 253 5-3/8 5.359 1/8 0.139 254 5-1/2 5.484 1/8 0.139 255 5-5/8 5.609 1/8 0.139 256 5-3/4 5.734 1/8 0.139 257 5-7/8 5.859 1/8 0.139 258 6 5.984 1/8 0.139 259 6-1/4 6.234 1/8 0.139 260 6-1/2 6.484 1/8 0.139 261 6-3/4 6.734 1/8 0.139 262 7 6.984 1/8 0.139 263 7-1/4 7.234 1/8 0.139 264 7-1/2 7.484 1/8 0.139 265 7-3/4 7.734 1/8 0.139 266 8 7.984 1/8 0.139 267 8-1/4 8.234 1/8 0.139 268 8-1/2 8.484 1/8 0.139 269 8-3/4 8.734 1/8 0.139 270 9 8.984 1/8 0.139 271 9-1/4 9.234 1/8 0.139 272 9-1/2 9.484 1/8 0.139 273 9-3/4 9.734 1/8 0.139 274 10 9.984 1/8 0.139 275 10-1/2 10.484 1/8 0.139 276 11 10.984 1/8 0.139 277 11-1/2 11.484 1/8 0.139 278 12 11.984 1/8 0.139 279 13 12.984 1/8 0.139 280 14 13.984 1/8 0.139 281 15 14.984 1/8 0.139 282 16 15.955 1/8 0.139 283 17 16.955 1/8 0.139 284 18 17.955 1/8 0.139 309 7/16 0.412 3/16 0.210 310 1/2 0.475 3/16 0.210 311 9/16 0.537 3/16 0.210 312 5/8 0.600 3/16 0.210 313 11/16 0.662 3/16 0.210 314 3/4 0.725 3/16 0.210 315 13/16 0.787 3/16 0.210 316 7/8 0.850 3/16 0.210 317 15/16 0.912 3/16 0.210 318 1 0.975 3/16 0.210 319 1-1/16 1.037 3/16 0.210 320 1-1/8 1.100 3/16 0.210 321 1-3/16 1.162 3/16 0.210 322 1-1/4 1.225 3/16 0.210 323 1-5/16 1.287 3/16 0.210 324 1-3/8 1.350 3/16 0.210 325 1-1/2 1.475 3/16 0.210 326 1-5/8 1.600 3/16 0.210 327 1-3/4 1.725 3/16 0.210 328 1-7/8 1.850 3/16 0.210 329 2 1.975 3/16 0.210 330 2-1/8 2.100 3/16 0.210 331 2-1/4 2.225 3/16 0.210 332 2-3/8 2.350 3/16 0.210 333 2-1/2 2.475 3/16 0.210 334 2-5/8 2.600 3/16 0.210 335 2-3/4 2.725 3/16 0.210 336 2-7/8 2.850 3/16 0.210 337 3 2.975 3/16 0.210 338 3-1/8 3.100 3/16 0.210 339 3-1/4 3.225 3/16 0.210 340 3-3/8 3.350 3/16 0.210 341 3-1/2 3.475 3/16 0.210 342 3-5/8 3.600 3/16 0.210 343 3-3/4 3.725 3/16 0.210 344 3-7/8 3.850 3/16 0.210 345 4 3.975 3/16 0.210 346 4-1/8 4.100 3/16 0.210 347 4-1/4 4.225 3/16 0.210 348 4-3/8 4.350 3/16 0.210 349 4-1/2 4.475 3/16 0.210 350 4-5/8 4.600 3/16 0.210 351 4-3/4 4.725 3/16 0.210 352 4-7/8 4.850 3/16 0.210 353 5 4.975 3/16 0.210 354 5-1/8 5.100 3/16 0.210 355 5-1/4 5.225 3/16 0.210 356 5-3/8 5.350 3/16 0.210 357 5-1/2 5.475 3/16 0.210 358 5-5/8 5.600 3/16 0.210 359 5-3/4 5.725 3/16 0.210 360 5-7/8 5.850 3/16 0.210 361 6 5.975 3/16 0.210 362 6-1/4 6.225 3/16 0.210 363 6-1/2 6.475 3/16 0.210 364 6-3/4 6.725 3/16 0.210 365 7 6.975 3/16 0.210 366 7-1/4 7.225 3/16 0.210 367 7-1/2 7.475 3/16 0.210 368 7-3/4 7.725 3/16 0.210 369 8 7.975 3/16 0.210 370 8-1/4 8.225 3/16 0.210 371 8-1/2 8.475 3/16 0.210 372 8-3/4 8.725 3/16 0.210 373 9 8.975 3/16 0.210 374 9-1/4 9.225 3/16 0.210 375 9-1/2 9.475 3/16 0.210 376 9-3/4 9.725 3/16 0.210 377 10 9.975 3/16 0.210 378 10-1/2 10.475 3/16 0.210 379 11 10.975 3/16 0.210 380 11-1/2 11.475 3/16 0.210 381 12 11.975 3/16 0.210 382 13 12.975 3/16 0.210 383 14 13.975 3/16 0.210 384 15 14.975 3/16 0.210 385 16 15.955 3/16 0.210 386 17 16.955 3/16 0.210 387 18 17.955 3/16 0.210 388 19 18.955 3/16 0.210 389 20 19.955 3/16 0.210 390 21 20.955 3/16 0.210 391 22 21.955 3/16 0.210 392 23 22.940 3/16 0.210 393 24 23.940 3/16 0.210 394 25 24.940 3/16 0.210 395 26 25.940 3/16 0.210 425 4-1/2 4.475 1/4 0.275 426 4-5/8 4.600 1/4 0.275 427 4-3/4 4.725 1/4 0.275 428 4-7/8 4.850 1/4 0.275 429 5 4.975 1/4 0.275 430 5-1/8 5.100 1/4 0.275 431 5-1/4 5.225 1/4 0.275 432 5-3/8 5.350 1/4 0.275 433 5-1/2 5.475 1/4 0.275 434 5-5/8 5.600 1/4 0.275 435 5-3/4 5.725 1/4 0.275 436 5-7/8 5.850 1/4 0.275 437 6 5.975 1/4 0.275 438 6-1/4 6.225 1/4 0.275 439 6-1/2 6.475 1/4 0.275 440 6-3/4 6.725 1/4 0.275 441 7 6.975 1/4 0.275 442 7-1/4 7.225 1/4 0.275 443 7-1/2 7.475 1/4 0.275 444 7-3/4 7.725 1/4 0.275 445 8 7.975 1/4 0.275 446 8-1/2 8.475 1/4 0.275 447 9 8.975 1/4 0.275 448 9-1/2 9.475 1/4 0.275 449 10 9.975 1/4 0.275 450 10-1/2 10.475 1/4 0.275 451 11 10.975 1/4 0.275 452 11-1/2 11.475 1/4 0.275 453 12 11.975 1/4 0.275 454 12-1/2 12.475 1/4 0.275 455 13 12.975 1/4 0.275 456 13-1/2 13.475 1/4 0.275 457 14 13.975 1/4 0.275 458 14-1/2 14.475 1/4 0.275 459 15 14.975 1/4 0.275 460 15-1/2 15.475 1/4 0.275 461 16 15.955 1/4 0.275 462 16-1/2 16.455 1/4 0.275 463 17 16.955 1/4 0.275 464 17-1/2 17.455 1/4 0.275 465 18 17.955 1/4 0.275 466 18-1/2 18.455 1/4 0.275 467 19 18.955 1/4 0.275 468 19-1/2 19.455 1/4 0.275 469 20 19.955 1/4 0.275 470 21 20.955 1/4 0.275 471 22 21.955 1/4 0.275 472 23 22.940 1/4 0.275 473 24 23.940 1/4 0.275 474 25 24.940 1/4 0.275 475 26 25.940 1/4 0.275   901 3/32 0.185   0.056 902 1/8 0.239   0.064 903 3/16 0.301   0.064 904 1/4 0.351   0.072 905 5/16 0.414   0.072 906 3/8 0.468   0.078 907 7/16 0.530   0.082 908 1/2 0.644   0.087 909 9/16 0.706   0.097 910 5/8 0.755   0.097 911 11/16 0.863   0.116 912 3/4 0.924   0.116 913 13/16 0.986   0.116 914 7/8 1.047   0.116 916 1 1.171   0.116 918 1-1/8 1.355   0.116 920 1-1/4 1.475   0.118 924 1-1/2 1.720   0.118 928 1-3/4 2.090   0.118 932 2 2.337   0.118

O-Ring Size Chart

O-Rings Size Chart for Standard O-Ring Dimensions

We supply all styles of O-rings. AS568 O-rings are an SAE standard most commonly used. Refer to the standard O-ring size chart below to help you find the AS568 O-ring size you need. Once you have the AS568 dash size you need, select a compound from the Chemical Compatibility table.

Should you have any questions, our team of applications engineers can help, contact us.