Roymech engineering encyclopedia

O-Rings – Sizes, Grooves and Seal Design


What is an O-ring seal?
An O-ring seal is a circular elastomer component used to prevent leakage between two surfaces. It works by deforming under compression to create a tight seal, commonly used in static and dynamic mechanical applications.

Need help selecting a seal or O-ring application? See the Seal Selection Guide for guidance on choosing between O-rings, rotary shaft seals, mechanical seals, packing and gaskets, and on the operating conditions that should be considered before using the detailed RoyMech seal data.

Important Note: The tables and information below are for reference only. The groove dimension and the associated information has been extracted from standards and catalogues. Selection of the O-ring parameters should include consideration of pressures, fluids, materials etc. Final details can only be completed using information from seal suppliers.

Introduction to O rings

O-ring seals are one of the most widely used sealing solutions in mechanical engineering due to their simplicity, reliability, and cost-effectiveness. They are used in hydraulic, pneumatic, and static sealing applications where preventing fluid or gas leakage is critical. Proper selection of O-ring size, material, and groove design is essential to ensure effective sealing performance and long service life.

An O- ring is basically defined by its section diameter and the inner diameter of the O-Ring.

O rings have many advantageous features including

  1. Low Cost
  2. Suit static and dynamic duties
  3. Space efficient
  4. Seals in both direction
  5. Fluid pressure assists sealing
  6. Suitable for all fluids-using appropriate elastomers

There are two current standards for O-rings in the UK

BS 1806:1989   Specification for dimensions of toroidal sealing rings ('O'-rings) and their housings (inch series).
Section sizes according to this standard include: 0.04in(1.02mm),  0.05inch(1.27mm),  0.06inch(1.52m),  0.07inch(1.78mm), 0.103inch(2.62mm),  0.139inch(3.53mm),  0.210inch(5.33mm), ,  0.275inch(6.99mm)

BS 4518:1982  Specification for metric dimensions of toroidal sealing rings ('O'-rings) and their housings
Section sizes according to this standard include: 1.6mm,  2.4mm,  3.0mm,  4.1mm,  5.7mm,  8.4mm


O-Ring Reference Number

According to BS4518 the O-Ring reference number =
O-Ring Inside dia (mm - 4 digits -1 decimal place)"-" O Ring Section (mm - 2 digits - 1 decimal place)
with the decimal point excluded.
For example 0545-30 is an O-ring of 54.5mm ID with 3.0 mm section


Surface Texture

The surface texture of the surfaces in contact with the O-ring seals should not exceed

  1. For Non Sealing surfaces 1.6 micrometers CLA
  2. For static applications 0.8 micrometers CLA
  3. For dynamic application 0.4 micrometers CLA

Notes:
Sealing surfaces are Rod, Hole, and bottom of groove.

For dynamic applications it is important not to have too good a surface finish(less than 0.2 micrometers) as a dry surface would result from the seal wiping action.


Static and Rotating Shaft Seals

Lead-In dia = Shaft dia (nom) - 2x C
Groove Dia max = Shaft Dia min + 2 x Fmax
Groove Dia min = Shaft Dia max + 2 x Fmin
Hole(Cyl) Dia max = Shaft Dia min + G		 Lead-In dia = Hole Dia (nom) + 2x C
Groove Dia Max = Hole dia min - 2 x Fmin
Groove Dia Min = Hole dia max - 2 x Fmax
Shaft Dia min = Hole Dia max - G

BS 4518 sizes For Dynamic Pneumatic and Hydraulic Applications

O-Ring Size 2.4mm 3.0mm 5.7mm 8.4mm
Width E 3.2/3.4 4.0/4.2 7.5/7.7 11/11.2
Radial Depth F
Hydraulic		 1.97/2.09 2.5/2.65 4.95/5.18 7.5/7.75
Radial Depth F
Pneumatic		 2.13/2.2 2.7/2.77 5.22/5.38 7.75/7.96
Max Clearance G 0.14 0.15 0.18 0.2
Lead_in C 0.6 0.7 1.0 1.2
Max Rad R 0.5 1.0 1.0 1.0

BS 4518 sizes For Static Applications

O-Ring Size 1.6mm 2.4mm 3.0mm 5.7mm 8.4mm
Width E 2.3/2.5 3.1/3.3 3.7/3.9 6.4/6.8 9.0/9.2
Radial Depth F 1.18/1.25 1.84/1.97 2.35/2.5 4.7/4.95 7.2/7.5
Max Clearance G 0.12 0.14 0.15 0.18 0.2
Lead_in C .6 0.7 0.8 1.2 1.5
Max Rad R 0.5 0.5 1.0 1.0 1.0


BS 4518 Sizes for Static Face Sealing Applications

- -

BS 4518 sizes For Face Seal Static Applications

O-Ring Size 1.6mm 2.4mm 3.0mm 5.7mm 8.4mm
Depth H 1.2/1.3 1.7/1.8 2.2/2.3 4.4/4.5 6.6/6.7
Max Rad R 0.2 0.5 1.0 1.0 1.0
Max Rad T 0.8 1.3 2.0 3.0 4.0
Chamfer- M 2.2/2.32 3.3/3.42 4.2/4.32 7.8/7.92 11.5/11.62
Min.Len L 4.0 5.0 6.0 10.0 14.0



O Ring Metric Sizes to BS4518

O-Ring Size 1.6mm 2.4mm 3.0mm 5.7mm 8.4mm


1.6mm O Ring

1.6mm +/- 0.08mm Dia O-ring
- Diameters Flange Groove Diameters
      Internal Pressure External Pressure
Ref. No Shaft Dia Hole(Cyl)Dia Vmax W(H11) V(h11) Wmin
0031-16 3.5 6 1 6.3 3.5 7.5
0041-16 4.5 7 2.3 7.3 4.5 8.5
0051-16 5.5 8 3.3 8.3 5.5 9.5
0061-16 6.5 9 4.3 9.3 6.5 10.5
0071-16 7.5 10 5.8 10.3 7.5 11.5
0081-16 8.5 11 6.8 11.3 8.5 12.5
0091-16 9.5 12 7.8 12.3 9.5 13.5
0101-16 10.5 13 8.8 13.3 10.5 14.5
0111-16 11.5 14 9.8 14.3 11.5 15.5
0121-16 12.5 15 10.8 15.3 12.5 16.5
0131-16 13.5 16 11.8 16.3 13.5 17.5
0141-16 14.5 17 12.8 17.3 14.5 18.5
0151-16 15.5 18 14 18.3 15.5 19.5
0161-16 16.5 19 15 19.3 16.5 20.5
0171-16 17.5 20 16 20.3 17.5 21.5
0181-16 18.5 21 17 21.3 18.5 22.5
0191-16 19.5 22 18 22.3 19.5 23.5
0221-16 22.5 25 21 25.3 22.5 26.5
0251-16 25.5 28 24 28.3 25.5 29.5
0271-16 27.5 30 26 30.3 27.5 31.5
0291-16 29.5 32 28 32.3 29.5 33.5
0321-16 32.5 35 31 35.3 32.5 36.5
0351-16 35.5 38 34 38.3 35.5 39.5
0371-16 37.5 40 36 40.3 37.5 41.5



2.4mm O Ring

2.4mm +/- 0.08mm Dia O-ring
- Diameters Flange Groove Diameters
Ref. No Shaft Dia Hole(Cyl)Dia Vmax W(H11) V(h11) Wmin
0036-24 4 8 - 8.4 4 10
0046-24 5 9 1 9.4 5 11
0056-24 6 10 2.5 10.4 6 12
0066-24 7 11 4 11.4 7 13
0076-24 8 12 5 12.4 8 14
0086-24 9 13 6.4 13.4 9 15
0096-24 10 14 7.4 14.4 10 16
0106-24 11 15 8.4 15.4 11 17
0116-24 12 16 9.5 16.4 12 18
0126-24 13 17 10.5 17.4 13 19
0136-24 14 18 11.5 18.4 14 20
0146-24 15 19 12.5 19.4 15 21
0156-24 16 20 13.5 20.4 16 22
0166-24 17 21 14.5 21.4 17 23
0176-24 18 22 15.5 22.4 18 24
0186-24 19 23 16.5 23.4 19 25
0196-24 20 24 17.5 24.4 20 26
0206-24 21 25 18.5 25.4 21 27
0216-24 22 26 19.5 26.4 22 28
0246-24 25 29 22.5 29.4 25 31
0276-24 28 32 25.5 32.4 28 34
0296-24 30 34 27.5 34.4 30 36
0316-24 32 36 29.5 36.4 32 38
0346-24 35 39 32.5 39.4 35 41
0356-24 36 40 33.5 40.4 36 42
0376-24 38 42 35.5 42.4 38 44
0396-24 40 44 37.5 44.4 40 46
0416-24 42 46 39.5 46.4 42 48
0446-24 45 49 42.5 49.4 45 51
0456-24 46 50 43.5 50.4 46 52
0476-24 48 52 45.5 52.4 48 54
0496-24 50 54 47.5 54.4 50 56
0516-24 52 56 49.5 56.4 52 58
0546-24 55 59 52.5 59.4 55 61
0556-24 56 60 53.5 60.4 56 62
0576-24 58 62 55.5 62.4 58 64
0586-24 59 63 56.5 63.4 59 65
0596-24 60 64 57.5 64.4 60 66
0616-24 62 66 59.5 66.4 62 68
0626-24 63 67 60.5 67.4 63 69
0646-24 65 69 62.5 69.4 65 71
0676-24 68 72 65.5 72.4 68 74
0696-24 70 74 67.5 74.4 70 76


3.0mm O Ring

3.0mm +/- 0.10mm Dia O-ring
-Diameters Flange Groove Diameters
Ref. No Shaft Dia Hole(Cyl)Dia Vmax W(H11) V(h11) Wmin
0195-30 20 25 17 25 20 28
0215-30 22 27 19 27 22 30
0225-30 23 28 20 28 23 31
0245-30 25 30 22 30 25 33
0255-30 26 31 23 31 26 34
0265-30 27 32 24 32 27 35
0275-30 28 33 25 33 28 36
0295-30 30 35 27 35 30 38
0315-30 32 37 29 37 32 40
0325-30 33 38 30 38 33 41
0345-30 35 40 32 40 35 43
0355-30 36 41 33 41 36 44
0365-30 37 42 34 42 37 45
0375-30 38 43 35 43 38 46
0395-30 40 45 37 45 40 48
0415-30 42 47 39 47 42 50
0425-30 43 48 40 48 43 51
0445-30 45 50 42 50 45 53
0495-30 50 55 47 55 50 58
0545-30 55 60 52 60 55 63
0555-30 56 61 53 61 56 64
0575-30 58 63 55 63 58 66
0595-30 60 65 57 65 60 68
0625-30 63 68 60 68 63 71
0645-30 65 70 62 70 65 73
0695-30 70 75 67 75 70 78
0745-30 75 80 72 80 75 83
0795-30 80 85 77 85 80 88
0845-30 85 90 82 90 85 93
0895-30 90 95 87 95 90 98
0945-30 95 100 92 100 95 103
0995-30 100 105 97 105 100 108
1045-30 105 110 102 110 105 113
1095-30 110 115 107 115 110 118
1145-30 115 120 112 120 115 123
1195-30 120 125 117 125 120 128
1245-30 125 130 122 130 125 133
1295-30 130 135 127 135 130 138
1345-30 135 140 132 140 135 143
1395-30 140 145 137 145 140 148
1445-30 145 150 142 150 145 153
1495-30 150 155 147 155 150 158
1545-30 155 160 152 160 155 163
1595-30 160 165 157 165 160 168
1645-30 165 170 162 170 165 173
1695-30 170 175 167 175 170 178
1745-30 175 180 172 180 175 183
1795-30 180 185 177 185 180 188
1845-30 185 190 182 190 185 193
1895-30 190 195 187 195 190 198
1945-30 195 200 192 200 195 203
1995-30 200 205 197 205 200 208
2095-30 210 215 207 215 210 218
2195-30 220 225 217 225 220 228
2295-30 230 235 227 235 230 238
2395-30 240 245 237 245 240 248
2445-30 245 250 242 250 245 253
2495-30 250 255 247 255 250 258


5.7mm O Ring

5.7mm +/- 0.12mm Dia O-ring
-Diameters Flange Groove Diameters
Ref. No Shaft Dia Hole(Cyl)Dia Vmax W(H11) V(h11) W min
0443-57 45 55 41 55 45 59
0453-57 46 56 42 56 46 60
0493-57 50 60 46 60 50 64
0523-57 53 63 49 63 53 67
0543-57 55 65 51 65 55 69
0553-57 56 66 52 66 56 70
0593-57 60 70 56 70 60 74
0623-57 63 73 59 73 63 77
0643-57 65 75 61 75 65 79
0693-57 70 80 66 80 70 84
0743-57 75 85 71 85 75 89
0793-57 80 90 76 90 80 94
0843-57 85 95 81 95 85 99
0893-57 90 100 86 100 90 104
0943-57 95 105 91 105 95 109
0993-57 100 110 96 110 100 114
1043-57 105 115 101 115 105 119
1093-57 110 120 106 120 110 124
1143-57 115 125 111 125 115 129
1193-57 120 130 116 130 120 134
1243-57 125 135 121 135 125 139
1293-57 130 140 126 140 130 144
1343-57 135 145 131 145 135 149
1393-57 140 150 136 150 140 154
1443-57 145 155 141 155 145 159
1493-57 150 160 146 160 150 164
1543-57 155 165 151 165 155 169
1593-57 160 170 156 170 160 174
1643-57 165 175 161 175 165 179
1693-57 170 180 166 180 170 184
1743-57 175 185 171 185 175 189
1793-57 180 190 176 190 180 194
1843-57 185 195 181 195 185 199
1893-57 190 200 186 199 190 204
1943-57 195 205 191 204 195 209
1993-57 200 210 195 209 200 214
2093-57 210 220 205 219 210 224
2193-57 220 230 215 229 220 234
2293-57 230 240 225 239 230 244
2393-57 240 250 235 249 240 254
2493-57 250 260 245 259 250 264
2593-57 260 270 255 269 261 275
2693-57 270 280 265 279 271 285
2793-57 280 290 275 289 281 295
2893-57 290 300 285 299 291 305
2993-57 300 310 295 309 301 315
3093-57 310 320 305 319 311 325
3193-57 320 330 315 329 321 335
3393-57 340 350 335 349 341 355
3593-57 360 370 355 369 361 375
3793-57 380 390 375 389 381 395
3893-57 390 400 385 399 391 405
3993-57 400 410 395 409 401 415
4193-57 420 430 415 429 422 436
4393-57 440 450 435 449 442 456
4593-57 460 470 455 469 462 476
4793-57 480 490 475 489 482 496
4893-57 490 500 485 499 492 506
4993-57 500 510 495 509 502 516




8.4mm O Ring

8.4mm +/- 0.15mm Dia O-ring
-Diameters Flange Groove Diameters
Ref. No Shaft Dia Hole(Cyl)Dia Vmax W(H11) V(h11) W min
1441-84 145 160 140 160 145 165
1491-84 150 165 145 165 150 170
1541-84 155 170 150 170 155 175
1591-84 160 175 155 175 160 180
1641-84 165 180 160 180 165 185
1691-84 170 185 165 185 170 190
1741-84 175 190 170 190 175 195
1791-84 180 195 175 195 180 200
1841-84 185 200 180 200 185 205
1891-84 190 205 185 205 190 210
1941-84 195 210 190 210 195 215
1991-84 200 215 195 215 200 220
2041-84 205 220 200 220 205 225
2091-84 210 225 205 225 210 230
2191-84 220 235 215 235 220 240
2291-84 230 245 225 245 230 250
2341-84 235 250 230 250 235 255
2391-84 240 255 235 255 240 260
2491-84 250 265 245 265 250 270


See Also


Links Providing information on O Ring Seals
  1. James Walker Well known UK Supplier
  2. Garlock A supplier of a wide range of seal products
  3. Supaseal -Lots of information and seal dimensions
  4. mdmetric Downloads including information on metric O-rings
  5. Trelleborg A supplier hompage including lots of useful technical information including an O -ring calculator