AS568 O-ring sizes are identified by a dash number: the first digit gives the cross-section series and the remaining digits the inside diameter. For example, -214 is a 0.984 in (24.99 mm) ID ring with a 0.139 in (3.53 mm) cross-section.
The AS568 standard (from SAE, used across North America and widely worldwide) lists 349 standard O-ring sizes from -001 to -475 in this chart, in five main cross-section series: 0.070, 0.103, 0.139, 0.210 and 0.275 in. Find your ring by dash number, by inside diameter (ID) or by cross-section (CS) with the search box; switch between inch and mm with the toggle. The outside diameter (OD) column is simply ID + 2 × CS, handy for checking a ring you have measured. Sizes are for the ring in its free state; a "2-" prefix (as in 2-214) is a common supplier way of writing the same AS568 size. To design the groove, use the O-Ring Groove Calculator.
The five AS568 cross-section series
| Series | Dash numbers | Cross-section (W) | CS tolerance | Typical use |
|---|---|---|---|---|
| -001 | single size | 0.040 in | ±.003 in | Very small sizes with their own cross-sections |
| -002 | single size | 0.050 in | ±.003 in | Very small sizes with their own cross-sections |
| -003 | single size | 0.060 in | ±.003 in | Very small sizes with their own cross-sections |
| 0xx | -004 to -050 | 0.070 in | ±.003 in | Small static seals, instrument fittings |
| 1xx | -102 to -178 | 0.103 in | ±.003 in | Small rods and pistons, light-duty static seals |
| 2xx | -201 to -284 | 0.139 in | ±.004 in | General hydraulic and pneumatic rods, pistons and face seals |
| 3xx | -309 to -395 | 0.210 in | ±.005 in | Larger hydraulic cylinders and higher pressure |
| 4xx | -425 to -475 | 0.275 in | ±.006 in | Large-diameter, heavy-section seals |
Within each series the dash number climbs with the ID, in 1/16 in steps for the small sizes, then 1/8, 1/4, 1/2 and 1 in steps for the larger sizes.
AS568 O-ring size chart (-001 to -475)
Type a whole dash number (214), or a size with a decimal point to find the closest IDs (in the units selected): 0.984 in inch mode, 25.0 in mm mode.
| AS568 dash no. | Inside diameter (ID) | Cross-section (W) ± tol. | Outside diameter (ref.) |
|---|---|---|---|
| -001 | 0.029 | 0.040 ±.003 | 0.109 |
| -002 | 0.042 | 0.050 ±.003 | 0.142 |
| -003 | 0.056 | 0.060 ±.003 | 0.176 |
| -004 | 0.070 | 0.070 ±.003 | 0.210 |
| -005 | 0.101 | 0.070 ±.003 | 0.241 |
| -006 | 0.114 | 0.070 ±.003 | 0.254 |
| -007 | 0.145 | 0.070 ±.003 | 0.285 |
| -008 | 0.176 | 0.070 ±.003 | 0.316 |
| -009 | 0.208 | 0.070 ±.003 | 0.348 |
| -010 | 0.239 | 0.070 ±.003 | 0.379 |
| -011 | 0.301 | 0.070 ±.003 | 0.441 |
| -012 | 0.364 | 0.070 ±.003 | 0.504 |
| -013 | 0.426 | 0.070 ±.003 | 0.566 |
| -014 | 0.489 | 0.070 ±.003 | 0.629 |
| -015 | 0.551 | 0.070 ±.003 | 0.691 |
| -016 | 0.614 | 0.070 ±.003 | 0.754 |
| -017 | 0.676 | 0.070 ±.003 | 0.816 |
| -018 | 0.739 | 0.070 ±.003 | 0.879 |
| -019 | 0.801 | 0.070 ±.003 | 0.941 |
| -020 | 0.864 | 0.070 ±.003 | 1.004 |
| -021 | 0.926 | 0.070 ±.003 | 1.066 |
| -022 | 0.989 | 0.070 ±.003 | 1.129 |
| -023 | 1.051 | 0.070 ±.003 | 1.191 |
| -024 | 1.114 | 0.070 ±.003 | 1.254 |
| -025 | 1.176 | 0.070 ±.003 | 1.316 |
| -026 | 1.239 | 0.070 ±.003 | 1.379 |
| -027 | 1.301 | 0.070 ±.003 | 1.441 |
| -028 | 1.364 | 0.070 ±.003 | 1.504 |
| -029 | 1.489 | 0.070 ±.003 | 1.629 |
| -030 | 1.614 | 0.070 ±.003 | 1.754 |
| -031 | 1.739 | 0.070 ±.003 | 1.879 |
| -032 | 1.864 | 0.070 ±.003 | 2.004 |
| -033 | 1.989 | 0.070 ±.003 | 2.129 |
| -034 | 2.114 | 0.070 ±.003 | 2.254 |
| -035 | 2.239 | 0.070 ±.003 | 2.379 |
| -036 | 2.364 | 0.070 ±.003 | 2.504 |
| -037 | 2.489 | 0.070 ±.003 | 2.629 |
| -038 | 2.614 | 0.070 ±.003 | 2.754 |
| -039 | 2.739 | 0.070 ±.003 | 2.879 |
| -040 | 2.864 | 0.070 ±.003 | 3.004 |
| -041 | 2.989 | 0.070 ±.003 | 3.129 |
| -042 | 3.239 | 0.070 ±.003 | 3.379 |
| -043 | 3.489 | 0.070 ±.003 | 3.629 |
| -044 | 3.739 | 0.070 ±.003 | 3.879 |
| -045 | 3.989 | 0.070 ±.003 | 4.129 |
| -046 | 4.239 | 0.070 ±.003 | 4.379 |
| -047 | 4.489 | 0.070 ±.003 | 4.629 |
| -048 | 4.739 | 0.070 ±.003 | 4.879 |
| -049 | 4.989 | 0.070 ±.003 | 5.129 |
| -050 | 5.239 | 0.070 ±.003 | 5.379 |
| -102 | 0.049 | 0.103 ±.003 | 0.255 |
| -103 | 0.081 | 0.103 ±.003 | 0.287 |
| -104 | 0.112 | 0.103 ±.003 | 0.318 |
| -105 | 0.143 | 0.103 ±.003 | 0.349 |
| -106 | 0.174 | 0.103 ±.003 | 0.380 |
| -107 | 0.206 | 0.103 ±.003 | 0.412 |
| -108 | 0.237 | 0.103 ±.003 | 0.443 |
| -109 | 0.299 | 0.103 ±.003 | 0.505 |
| -110 | 0.362 | 0.103 ±.003 | 0.568 |
| -111 | 0.424 | 0.103 ±.003 | 0.630 |
| -112 | 0.487 | 0.103 ±.003 | 0.693 |
| -113 | 0.549 | 0.103 ±.003 | 0.755 |
| -114 | 0.612 | 0.103 ±.003 | 0.818 |
| -115 | 0.674 | 0.103 ±.003 | 0.880 |
| -116 | 0.737 | 0.103 ±.003 | 0.943 |
| -117 | 0.799 | 0.103 ±.003 | 1.005 |
| -118 | 0.862 | 0.103 ±.003 | 1.068 |
| -119 | 0.924 | 0.103 ±.003 | 1.130 |
| -120 | 0.987 | 0.103 ±.003 | 1.193 |
| -121 | 1.049 | 0.103 ±.003 | 1.255 |
| -122 | 1.112 | 0.103 ±.003 | 1.318 |
| -123 | 1.174 | 0.103 ±.003 | 1.380 |
| -124 | 1.237 | 0.103 ±.003 | 1.443 |
| -125 | 1.299 | 0.103 ±.003 | 1.505 |
| -126 | 1.362 | 0.103 ±.003 | 1.568 |
| -127 | 1.424 | 0.103 ±.003 | 1.630 |
| -128 | 1.487 | 0.103 ±.003 | 1.693 |
| -129 | 1.549 | 0.103 ±.003 | 1.755 |
| -130 | 1.612 | 0.103 ±.003 | 1.818 |
| -131 | 1.674 | 0.103 ±.003 | 1.880 |
| -132 | 1.737 | 0.103 ±.003 | 1.943 |
| -133 | 1.799 | 0.103 ±.003 | 2.005 |
| -134 | 1.862 | 0.103 ±.003 | 2.068 |
| -135 | 1.924 | 0.103 ±.003 | 2.130 |
| -136 | 1.987 | 0.103 ±.003 | 2.193 |
| -137 | 2.049 | 0.103 ±.003 | 2.255 |
| -138 | 2.112 | 0.103 ±.003 | 2.318 |
| -139 | 2.174 | 0.103 ±.003 | 2.380 |
| -140 | 2.237 | 0.103 ±.003 | 2.443 |
| -141 | 2.299 | 0.103 ±.003 | 2.505 |
| -142 | 2.362 | 0.103 ±.003 | 2.568 |
| -143 | 2.424 | 0.103 ±.003 | 2.630 |
| -144 | 2.487 | 0.103 ±.003 | 2.693 |
| -145 | 2.549 | 0.103 ±.003 | 2.755 |
| -146 | 2.612 | 0.103 ±.003 | 2.818 |
| -147 | 2.674 | 0.103 ±.003 | 2.880 |
| -148 | 2.737 | 0.103 ±.003 | 2.943 |
| -149 | 2.799 | 0.103 ±.003 | 3.005 |
| -150 | 2.862 | 0.103 ±.003 | 3.068 |
| -151 | 3.112 | 0.103 ±.003 | 3.318 |
| -152 | 3.362 | 0.103 ±.003 | 3.568 |
| -153 | 3.612 | 0.103 ±.003 | 3.818 |
| -154 | 3.862 | 0.103 ±.003 | 4.068 |
| -155 | 4.112 | 0.103 ±.003 | 4.318 |
| -156 | 4.362 | 0.103 ±.003 | 4.568 |
| -157 | 4.612 | 0.103 ±.003 | 4.818 |
| -158 | 4.862 | 0.103 ±.003 | 5.068 |
| -159 | 5.112 | 0.103 ±.003 | 5.318 |
| -160 | 5.362 | 0.103 ±.003 | 5.568 |
| -161 | 5.612 | 0.103 ±.003 | 5.818 |
| -162 | 5.862 | 0.103 ±.003 | 6.068 |
| -163 | 6.112 | 0.103 ±.003 | 6.318 |
| -164 | 6.362 | 0.103 ±.003 | 6.568 |
| -165 | 6.612 | 0.103 ±.003 | 6.818 |
| -166 | 6.862 | 0.103 ±.003 | 7.068 |
| -167 | 7.112 | 0.103 ±.003 | 7.318 |
| -168 | 7.362 | 0.103 ±.003 | 7.568 |
| -169 | 7.612 | 0.103 ±.003 | 7.818 |
| -170 | 7.862 | 0.103 ±.003 | 8.068 |
| -171 | 8.112 | 0.103 ±.003 | 8.318 |
| -172 | 8.362 | 0.103 ±.003 | 8.568 |
| -173 | 8.612 | 0.103 ±.003 | 8.818 |
| -174 | 8.862 | 0.103 ±.003 | 9.068 |
| -175 | 9.112 | 0.103 ±.003 | 9.318 |
| -176 | 9.362 | 0.103 ±.003 | 9.568 |
| -177 | 9.612 | 0.103 ±.003 | 9.818 |
| -178 | 9.862 | 0.103 ±.003 | 10.068 |
| -201 | 0.171 | 0.139 ±.004 | 0.449 |
| -202 | 0.234 | 0.139 ±.004 | 0.512 |
| -203 | 0.296 | 0.139 ±.004 | 0.574 |
| -204 | 0.359 | 0.139 ±.004 | 0.637 |
| -205 | 0.421 | 0.139 ±.004 | 0.699 |
| -206 | 0.484 | 0.139 ±.004 | 0.762 |
| -207 | 0.546 | 0.139 ±.004 | 0.824 |
| -208 | 0.609 | 0.139 ±.004 | 0.887 |
| -209 | 0.671 | 0.139 ±.004 | 0.949 |
| -210 | 0.734 | 0.139 ±.004 | 1.012 |
| -211 | 0.796 | 0.139 ±.004 | 1.074 |
| -212 | 0.859 | 0.139 ±.004 | 1.137 |
| -213 | 0.921 | 0.139 ±.004 | 1.199 |
| -214 | 0.984 | 0.139 ±.004 | 1.262 |
| -215 | 1.046 | 0.139 ±.004 | 1.324 |
| -216 | 1.109 | 0.139 ±.004 | 1.387 |
| -217 | 1.171 | 0.139 ±.004 | 1.449 |
| -218 | 1.234 | 0.139 ±.004 | 1.512 |
| -219 | 1.296 | 0.139 ±.004 | 1.574 |
| -220 | 1.359 | 0.139 ±.004 | 1.637 |
| -221 | 1.421 | 0.139 ±.004 | 1.699 |
| -222 | 1.484 | 0.139 ±.004 | 1.762 |
| -223 | 1.609 | 0.139 ±.004 | 1.887 |
| -224 | 1.734 | 0.139 ±.004 | 2.012 |
| -225 | 1.859 | 0.139 ±.004 | 2.137 |
| -226 | 1.984 | 0.139 ±.004 | 2.262 |
| -227 | 2.109 | 0.139 ±.004 | 2.387 |
| -228 | 2.234 | 0.139 ±.004 | 2.512 |
| -229 | 2.359 | 0.139 ±.004 | 2.637 |
| -230 | 2.484 | 0.139 ±.004 | 2.762 |
| -231 | 2.609 | 0.139 ±.004 | 2.887 |
| -232 | 2.734 | 0.139 ±.004 | 3.012 |
| -233 | 2.859 | 0.139 ±.004 | 3.137 |
| -234 | 2.984 | 0.139 ±.004 | 3.262 |
| -235 | 3.109 | 0.139 ±.004 | 3.387 |
| -236 | 3.234 | 0.139 ±.004 | 3.512 |
| -237 | 3.359 | 0.139 ±.004 | 3.637 |
| -238 | 3.484 | 0.139 ±.004 | 3.762 |
| -239 | 3.609 | 0.139 ±.004 | 3.887 |
| -240 | 3.734 | 0.139 ±.004 | 4.012 |
| -241 | 3.859 | 0.139 ±.004 | 4.137 |
| -242 | 3.984 | 0.139 ±.004 | 4.262 |
| -243 | 4.109 | 0.139 ±.004 | 4.387 |
| -244 | 4.234 | 0.139 ±.004 | 4.512 |
| -245 | 4.359 | 0.139 ±.004 | 4.637 |
| -246 | 4.484 | 0.139 ±.004 | 4.762 |
| -247 | 4.609 | 0.139 ±.004 | 4.887 |
| -248 | 4.734 | 0.139 ±.004 | 5.012 |
| -249 | 4.859 | 0.139 ±.004 | 5.137 |
| -250 | 4.984 | 0.139 ±.004 | 5.262 |
| -251 | 5.109 | 0.139 ±.004 | 5.387 |
| -252 | 5.234 | 0.139 ±.004 | 5.512 |
| -253 | 5.359 | 0.139 ±.004 | 5.637 |
| -254 | 5.484 | 0.139 ±.004 | 5.762 |
| -255 | 5.609 | 0.139 ±.004 | 5.887 |
| -256 | 5.734 | 0.139 ±.004 | 6.012 |
| -257 | 5.859 | 0.139 ±.004 | 6.137 |
| -258 | 5.984 | 0.139 ±.004 | 6.262 |
| -259 | 6.234 | 0.139 ±.004 | 6.512 |
| -260 | 6.484 | 0.139 ±.004 | 6.762 |
| -261 | 6.734 | 0.139 ±.004 | 7.012 |
| -262 | 6.984 | 0.139 ±.004 | 7.262 |
| -263 | 7.234 | 0.139 ±.004 | 7.512 |
| -264 | 7.484 | 0.139 ±.004 | 7.762 |
| -265 | 7.734 | 0.139 ±.004 | 8.012 |
| -266 | 7.984 | 0.139 ±.004 | 8.262 |
| -267 | 8.234 | 0.139 ±.004 | 8.512 |
| -268 | 8.484 | 0.139 ±.004 | 8.762 |
| -269 | 8.734 | 0.139 ±.004 | 9.012 |
| -270 | 8.984 | 0.139 ±.004 | 9.262 |
| -271 | 9.234 | 0.139 ±.004 | 9.512 |
| -272 | 9.484 | 0.139 ±.004 | 9.762 |
| -273 | 9.734 | 0.139 ±.004 | 10.012 |
| -274 | 9.984 | 0.139 ±.004 | 10.262 |
| -275 | 10.484 | 0.139 ±.004 | 10.762 |
| -276 | 10.984 | 0.139 ±.004 | 11.262 |
| -277 | 11.484 | 0.139 ±.004 | 11.762 |
| -278 | 11.984 | 0.139 ±.004 | 12.262 |
| -279 | 12.984 | 0.139 ±.004 | 13.262 |
| -280 | 13.984 | 0.139 ±.004 | 14.262 |
| -281 | 14.984 | 0.139 ±.004 | 15.262 |
| -282 | 15.955 | 0.139 ±.004 | 16.233 |
| -283 | 16.955 | 0.139 ±.004 | 17.233 |
| -284 | 17.955 | 0.139 ±.004 | 18.233 |
| -309 | 0.412 | 0.210 ±.005 | 0.832 |
| -310 | 0.475 | 0.210 ±.005 | 0.895 |
| -311 | 0.537 | 0.210 ±.005 | 0.957 |
| -312 | 0.600 | 0.210 ±.005 | 1.020 |
| -313 | 0.662 | 0.210 ±.005 | 1.082 |
| -314 | 0.725 | 0.210 ±.005 | 1.145 |
| -315 | 0.787 | 0.210 ±.005 | 1.207 |
| -316 | 0.850 | 0.210 ±.005 | 1.270 |
| -317 | 0.912 | 0.210 ±.005 | 1.332 |
| -318 | 0.975 | 0.210 ±.005 | 1.395 |
| -319 | 1.037 | 0.210 ±.005 | 1.457 |
| -320 | 1.100 | 0.210 ±.005 | 1.520 |
| -321 | 1.162 | 0.210 ±.005 | 1.582 |
| -322 | 1.225 | 0.210 ±.005 | 1.645 |
| -323 | 1.287 | 0.210 ±.005 | 1.707 |
| -324 | 1.350 | 0.210 ±.005 | 1.770 |
| -325 | 1.475 | 0.210 ±.005 | 1.895 |
| -326 | 1.600 | 0.210 ±.005 | 2.020 |
| -327 | 1.725 | 0.210 ±.005 | 2.145 |
| -328 | 1.850 | 0.210 ±.005 | 2.270 |
| -329 | 1.975 | 0.210 ±.005 | 2.395 |
| -330 | 2.100 | 0.210 ±.005 | 2.520 |
| -331 | 2.225 | 0.210 ±.005 | 2.645 |
| -332 | 2.350 | 0.210 ±.005 | 2.770 |
| -333 | 2.475 | 0.210 ±.005 | 2.895 |
| -334 | 2.600 | 0.210 ±.005 | 3.020 |
| -335 | 2.725 | 0.210 ±.005 | 3.145 |
| -336 | 2.850 | 0.210 ±.005 | 3.270 |
| -337 | 2.975 | 0.210 ±.005 | 3.395 |
| -338 | 3.100 | 0.210 ±.005 | 3.520 |
| -339 | 3.225 | 0.210 ±.005 | 3.645 |
| -340 | 3.350 | 0.210 ±.005 | 3.770 |
| -341 | 3.475 | 0.210 ±.005 | 3.895 |
| -342 | 3.600 | 0.210 ±.005 | 4.020 |
| -343 | 3.725 | 0.210 ±.005 | 4.145 |
| -344 | 3.850 | 0.210 ±.005 | 4.270 |
| -345 | 3.975 | 0.210 ±.005 | 4.395 |
| -346 | 4.100 | 0.210 ±.005 | 4.520 |
| -347 | 4.225 | 0.210 ±.005 | 4.645 |
| -348 | 4.350 | 0.210 ±.005 | 4.770 |
| -349 | 4.475 | 0.210 ±.005 | 4.895 |
| -350 | 4.600 | 0.210 ±.005 | 5.020 |
| -351 | 4.725 | 0.210 ±.005 | 5.145 |
| -352 | 4.850 | 0.210 ±.005 | 5.270 |
| -353 | 4.975 | 0.210 ±.005 | 5.395 |
| -354 | 5.100 | 0.210 ±.005 | 5.520 |
| -355 | 5.225 | 0.210 ±.005 | 5.645 |
| -356 | 5.350 | 0.210 ±.005 | 5.770 |
| -357 | 5.475 | 0.210 ±.005 | 5.895 |
| -358 | 5.600 | 0.210 ±.005 | 6.020 |
| -359 | 5.725 | 0.210 ±.005 | 6.145 |
| -360 | 5.850 | 0.210 ±.005 | 6.270 |
| -361 | 5.975 | 0.210 ±.005 | 6.395 |
| -362 | 6.225 | 0.210 ±.005 | 6.645 |
| -363 | 6.475 | 0.210 ±.005 | 6.895 |
| -364 | 6.725 | 0.210 ±.005 | 7.145 |
| -365 | 6.975 | 0.210 ±.005 | 7.395 |
| -366 | 7.225 | 0.210 ±.005 | 7.645 |
| -367 | 7.475 | 0.210 ±.005 | 7.895 |
| -368 | 7.725 | 0.210 ±.005 | 8.145 |
| -369 | 7.975 | 0.210 ±.005 | 8.395 |
| -370 | 8.225 | 0.210 ±.005 | 8.645 |
| -371 | 8.475 | 0.210 ±.005 | 8.895 |
| -372 | 8.725 | 0.210 ±.005 | 9.145 |
| -373 | 8.975 | 0.210 ±.005 | 9.395 |
| -374 | 9.225 | 0.210 ±.005 | 9.645 |
| -375 | 9.475 | 0.210 ±.005 | 9.895 |
| -376 | 9.725 | 0.210 ±.005 | 10.145 |
| -377 | 9.975 | 0.210 ±.005 | 10.395 |
| -378 | 10.475 | 0.210 ±.005 | 10.895 |
| -379 | 10.975 | 0.210 ±.005 | 11.395 |
| -380 | 11.475 | 0.210 ±.005 | 11.895 |
| -381 | 11.975 | 0.210 ±.005 | 12.395 |
| -382 | 12.975 | 0.210 ±.005 | 13.395 |
| -383 | 13.975 | 0.210 ±.005 | 14.395 |
| -384 | 14.975 | 0.210 ±.005 | 15.395 |
| -385 | 15.955 | 0.210 ±.005 | 16.375 |
| -386 | 16.955 | 0.210 ±.005 | 17.375 |
| -387 | 17.955 | 0.210 ±.005 | 18.375 |
| -388 | 18.955 | 0.210 ±.005 | 19.375 |
| -389 | 19.955 | 0.210 ±.005 | 20.375 |
| -390 | 20.955 | 0.210 ±.005 | 21.375 |
| -391 | 21.955 | 0.210 ±.005 | 22.375 |
| -392 | 22.940 | 0.210 ±.005 | 23.360 |
| -393 | 23.940 | 0.210 ±.005 | 24.360 |
| -394 | 24.940 | 0.210 ±.005 | 25.360 |
| -395 | 25.940 | 0.210 ±.005 | 26.360 |
| -425 | 4.475 | 0.275 ±.006 | 5.025 |
| -426 | 4.600 | 0.275 ±.006 | 5.150 |
| -427 | 4.725 | 0.275 ±.006 | 5.275 |
| -428 | 4.850 | 0.275 ±.006 | 5.400 |
| -429 | 4.975 | 0.275 ±.006 | 5.525 |
| -430 | 5.100 | 0.275 ±.006 | 5.650 |
| -431 | 5.225 | 0.275 ±.006 | 5.775 |
| -432 | 5.350 | 0.275 ±.006 | 5.900 |
| -433 | 5.475 | 0.275 ±.006 | 6.025 |
| -434 | 5.600 | 0.275 ±.006 | 6.150 |
| -435 | 5.725 | 0.275 ±.006 | 6.275 |
| -436 | 5.850 | 0.275 ±.006 | 6.400 |
| -437 | 5.975 | 0.275 ±.006 | 6.525 |
| -438 | 6.225 | 0.275 ±.006 | 6.775 |
| -439 | 6.475 | 0.275 ±.006 | 7.025 |
| -440 | 6.725 | 0.275 ±.006 | 7.275 |
| -441 | 6.975 | 0.275 ±.006 | 7.525 |
| -442 | 7.225 | 0.275 ±.006 | 7.775 |
| -443 | 7.475 | 0.275 ±.006 | 8.025 |
| -444 | 7.725 | 0.275 ±.006 | 8.275 |
| -445 | 7.975 | 0.275 ±.006 | 8.525 |
| -446 | 8.475 | 0.275 ±.006 | 9.025 |
| -447 | 8.975 | 0.275 ±.006 | 9.525 |
| -448 | 9.475 | 0.275 ±.006 | 10.025 |
| -449 | 9.975 | 0.275 ±.006 | 10.525 |
| -450 | 10.475 | 0.275 ±.006 | 11.025 |
| -451 | 10.975 | 0.275 ±.006 | 11.525 |
| -452 | 11.475 | 0.275 ±.006 | 12.025 |
| -453 | 11.975 | 0.275 ±.006 | 12.525 |
| -454 | 12.475 | 0.275 ±.006 | 13.025 |
| -455 | 12.975 | 0.275 ±.006 | 13.525 |
| -456 | 13.475 | 0.275 ±.006 | 14.025 |
| -457 | 13.975 | 0.275 ±.006 | 14.525 |
| -458 | 14.475 | 0.275 ±.006 | 15.025 |
| -459 | 14.975 | 0.275 ±.006 | 15.525 |
| -460 | 15.475 | 0.275 ±.006 | 16.025 |
| -461 | 15.955 | 0.275 ±.006 | 16.505 |
| -462 | 16.455 | 0.275 ±.006 | 17.005 |
| -463 | 16.955 | 0.275 ±.006 | 17.505 |
| -464 | 17.455 | 0.275 ±.006 | 18.005 |
| -465 | 17.955 | 0.275 ±.006 | 18.505 |
| -466 | 18.455 | 0.275 ±.006 | 19.005 |
| -467 | 18.955 | 0.275 ±.006 | 19.505 |
| -468 | 19.455 | 0.275 ±.006 | 20.005 |
| -469 | 19.955 | 0.275 ±.006 | 20.505 |
| -470 | 20.955 | 0.275 ±.006 | 21.505 |
| -471 | 21.955 | 0.275 ±.006 | 22.505 |
| -472 | 22.940 | 0.275 ±.006 | 23.490 |
| -473 | 23.940 | 0.275 ±.006 | 24.490 |
| -474 | 24.940 | 0.275 ±.006 | 25.490 |
| -475 | 25.940 | 0.275 ±.006 | 26.490 |
Inch values are AS568 nominal sizes; mm values are × 25.4, rounded to 0.01 mm. ID tolerances grow with size (from about ±0.004 in on the smallest rings) and are not listed here; check AS568 or your supplier for them. OD is calculated as ID + 2 × CS for reference.
How to use this chart
- Know the dash number? Type it in the search box (e.g. 214) to see the ID and CS.
- Measuring an unknown ring? Measure the cross-section first with a caliper, gently, without squashing it. That tells you the series. Then measure the ID (or OD) and type it with a decimal point to list the closest sizes. A ring that has been in service may have swollen or taken a set, so expect it to be slightly off nominal.
- Designing a seal? Choose the cross-section first (bigger is more forgiving and lasts longer; smaller saves space), then the ID. For a piston (OD) seal the ring is usually stretched slightly onto the groove; for a rod (ID) seal it is usually compressed slightly in its housing.
Worked example: a 1.500 in bore piston using the 0.139 in cross-section. With a typical gland depth of about 0.111 in, the groove (root) diameter is 1.500 − 2 × 0.111 = 1.278 in. Pick the ring with the nearest ID just below that so it stretches slightly into the groove: -218 (1.234 in ID × 0.139 in), about 3.6% stretch. Confirm squeeze, stretch and groove fill with the O-Ring Groove Calculator.
Metric O-rings (ISO 3601)
ISO 3601-1 covers O-ring sizes worldwide. It includes the AS568 inch sizes (shown here in mm) and also a metric series with cross-sections of 1.80, 2.65, 3.55, 5.30 and 7.00 mm. These are close to the AS568 sections (1.78, 2.62, 3.53, 5.33, 6.99 mm) but not identical, so do not mix them in a precise groove without checking squeeze. Many other metric rings (for example 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0 mm cross-sections) are sold by ID × CS, such as "20 × 2"; they are not AS568 sizes. When ordering a metric ring, quote ID × CS in mm plus the material and hardness (e.g. NBR 70 Shore A).
Related calculators and charts
- O-Ring Groove Calculator: gland depth, groove width, squeeze and stretch.
- ISO Tolerance Fit Calculator: bore and shaft tolerances for the housing.
- Surface Finish Converter: groove and bore finish for seals.
- Thermal Expansion Calculator: size change of the housing with temperature.
- Keyway and Key Size Chart, Socket Head Cap Screw Reference and Tap & Drill Size Reference.
Frequently asked questions
An AS568-214 O-ring has an inside diameter of 0.984 in (24.99 mm) and a cross-section of 0.139 in (3.53 mm), with a cross-section tolerance of ±0.004 in. Its outside diameter is about 1.262 in (32.05 mm).
The first digit is the cross-section series: 0 = 0.070 in, 1 = 0.103 in, 2 = 0.139 in, 3 = 0.210 in and 4 = 0.275 in (the three very small sizes -001 to -003 have their own sections). The other two digits count up with the inside diameter within that series.
Measure the cross-section with a caliper, without squeezing the ring, to find its series. Then measure the inside diameter, or lay the ring flat and measure the outside diameter and subtract two cross-sections. Look up the closest ID in that series. Used rings may be swollen or flattened, so allow for that.
No. ISO 3601-1 includes the AS568 inch sizes, but the metric series uses cross-sections of 1.80, 2.65, 3.55, 5.30 and 7.00 mm, which are close to but not the same as the AS568 sections of 1.78, 2.62, 3.53, 5.33 and 6.99 mm. Many other metric rings are sold simply by ID × CS.
The 2- prefix is a common supplier and Parker-style way of writing an AS568 size, so 2-214 is the same ring as AS568-214. Material and hardness are given separately, for example N70 or NBR 70 Shore A.
Source: SAE AS568 (aerospace size standard for O-rings), nominal ID and cross-section with cross-section tolerances; ISO 3601-1 for the metric note. The -9xx tube-fitting (boss) sizes are not included. Always check critical values against the current standard or the O-ring manufacturer's data.