BS 4518 O-Ring Size Chart

BS 4518 British metric O-Ring size chart with ID, CS, and OD in millimeters and inches, plus background on the BS 4518 standard.

History of BS 4518 Master O-Ring Size Chart Metric / ISO Chart

BS 4518 is the British Standards Institution metric O-Ring size system. Sizes are ID × CS in millimeters (store CS×ID codes), unlike legacy imperial BS 1806 dashes.

OD = ID + 2×CS. Code links open a product search on theoringstore.com.

205 sizes · BS 4518

1.6 mm cross-section

CS 1.6 mm · 26 sizes

BS 4518 1.6 mm cross-section size table
Code (CS×ID)	ID (mm)	CS (mm)	OD (mm)	ID (in)	CS (in)	OD (in)
1.60X003.1	3.10 ±0.15	1.60 ±0.08	6.30	0.122 ±.006	0.063 ±.003	0.248
1.60X004.1	4.10 ±0.15	1.60 ±0.08	7.30	0.161 ±.006	0.063 ±.003	0.287
1.60X005.1	5.10 ±0.15	1.60 ±0.08	8.30	0.201 ±.006	0.063 ±.003	0.327
1.60X006.1	6.10 ±0.15	1.60 ±0.08	9.30	0.240 ±.006	0.063 ±.003	0.366
1.60X007.1	7.10 ±0.15	1.60 ±0.08	10.30	0.280 ±.006	0.063 ±.003	0.406
1.60X008.1	8.10 ±0.15	1.60 ±0.08	11.30	0.319 ±.006	0.063 ±.003	0.445
1.60X009.1	9.10 ±0.15	1.60 ±0.08	12.30	0.358 ±.006	0.063 ±.003	0.484
1.60X010.1	10.10 ±0.20	1.60 ±0.08	13.30	0.398 ±.008	0.063 ±.003	0.524
1.60X011.1	11.10 ±0.20	1.60 ±0.08	14.30	0.437 ±.008	0.063 ±.003	0.563
1.60X012.1	12.10 ±0.20	1.60 ±0.08	15.30	0.476 ±.008	0.063 ±.003	0.602
1.60X013.1	13.10 ±0.20	1.60 ±0.08	16.30	0.516 ±.008	0.063 ±.003	0.642
1.60X014.1	14.10 ±0.20	1.60 ±0.08	17.30	0.555 ±.008	0.063 ±.003	0.681
1.60X015.1	15.10 ±0.20	1.60 ±0.08	18.30	0.595 ±.008	0.063 ±.003	0.721
1.60X016.1	16.10 ±0.20	1.60 ±0.08	19.30	0.634 ±.008	0.063 ±.003	0.760
1.60X017.1	17.10 ±0.20	1.60 ±0.08	20.30	0.673 ±.008	0.063 ±.003	0.799
1.60X018.1	18.10 ±0.25	1.60 ±0.08	21.30	0.713 ±.010	0.063 ±.003	0.839
1.60X019.1	19.10 ±0.25	1.60 ±0.08	22.30	0.752 ±.010	0.063 ±.003	0.878
1.60X020.1	20.10 ±0.25	1.60 ±0.08	23.30	0.791 ±.010	0.063 ±.003	0.917
1.60X021.1	21.10 ±0.25	1.60 ±0.08	24.30	0.831 ±.010	0.063 ±.003	0.957
1.60X022.1	22.10 ±0.25	1.60 ±0.08	25.30	0.870 ±.010	0.063 ±.003	0.996
1.60X025.1	25.10 ±0.25	1.60 ±0.08	28.30	0.988 ±.010	0.063 ±.003	1.114
1.60X027.1	27.10 ±0.25	1.60 ±0.08	30.30	1.067 ±.010	0.063 ±.003	1.193
1.60X029.1	29.10 ±0.25	1.60 ±0.08	32.30	1.146 ±.010	0.063 ±.003	1.272
1.60X032.1	32.10 ±0.35	1.60 ±0.08	35.30	1.264 ±.014	0.063 ±.003	1.390
1.60X035.1	35.10 ±0.35	1.60 ±0.08	38.30	1.382 ±.014	0.063 ±.003	1.508
1.60X037.1	37.10 ±0.35	1.60 ±0.08	40.30	1.461 ±.014	0.063 ±.003	1.587

2.4 mm cross-section

CS 2.4 mm · 43 sizes

BS 4518 2.4 mm cross-section size table
Code (CS×ID)	ID (mm)	CS (mm)	OD (mm)	ID (in)	CS (in)	OD (in)
2.40X003.6	3.60 ±0.15	2.40 ±0.09	8.40	0.142 ±.006	0.094 ±.004	0.330
2.40X004.6	4.60 ±0.15	2.40 ±0.09	9.40	0.181 ±.006	0.094 ±.004	0.369
2.40X005.6	5.60 ±0.15	2.40 ±0.09	10.40	0.221 ±.006	0.094 ±.004	0.408
2.40X006.6	6.60 ±0.15	2.40 ±0.09	11.40	0.260 ±.006	0.094 ±.004	0.448
2.40X007.6	7.60 ±0.15	2.40 ±0.09	12.40	0.299 ±.006	0.094 ±.004	0.487
2.40X008.6	8.60 ±0.15	2.40 ±0.09	13.40	0.339 ±.006	0.094 ±.004	0.527
2.40X009.6	9.60 ±0.15	2.40 ±0.09	14.40	0.378 ±.006	0.094 ±.004	0.566
2.40X010.6	10.60 ±0.20	2.40 ±0.09	15.40	0.417 ±.008	0.094 ±.004	0.605
2.40X011.6	11.60 ±0.20	2.40 ±0.09	16.40	0.457 ±.008	0.094 ±.004	0.645
2.40X012.6	12.60 ±0.20	2.40 ±0.09	17.40	0.496 ±.008	0.094 ±.004	0.684
2.40X013.6	13.60 ±0.20	2.40 ±0.09	18.40	0.535 ±.008	0.094 ±.004	0.723
2.40X014.6	14.60 ±0.20	2.40 ±0.09	19.40	0.575 ±.008	0.094 ±.004	0.763
2.40X015.6	15.60 ±0.20	2.40 ±0.09	20.40	0.614 ±.008	0.094 ±.004	0.802
2.40X016.6	16.60 ±0.20	2.40 ±0.09	21.40	0.653 ±.008	0.094 ±.004	0.841
2.40X017.6	17.60 ±0.20	2.40 ±0.09	22.40	0.693 ±.008	0.094 ±.004	0.881
2.40X018.6	18.60 ±0.25	2.40 ±0.09	23.40	0.732 ±.010	0.094 ±.004	0.920
2.40X019.6	19.60 ±0.25	2.40 ±0.09	24.40	0.772 ±.010	0.094 ±.004	0.960
2.40X020.6	20.60 ±0.25	2.40 ±0.09	25.40	0.811 ±.010	0.094 ±.004	0.999
2.40X021.6	21.60 ±0.25	2.40 ±0.09	26.40	0.850 ±.010	0.094 ±.004	1.038
2.40X024.6	24.60 ±0.25	2.40 ±0.09	29.40	0.969 ±.010	0.094 ±.004	1.157
2.40X027.6	27.60 ±0.25	2.40 ±0.09	32.40	1.087 ±.010	0.094 ±.004	1.275
2.40X029.6	29.60 ±0.25	2.40 ±0.09	34.40	1.165 ±.010	0.094 ±.004	1.353
2.40X031.6	31.60 ±0.35	2.40 ±0.09	36.40	1.244 ±.014	0.094 ±.004	1.432
2.40X034.6	34.60 ±0.35	2.40 ±0.09	39.40	1.362 ±.014	0.094 ±.004	1.550
2.40X035.6	35.60 ±0.35	2.40 ±0.09	40.40	1.402 ±.014	0.094 ±.004	1.590
2.40X037.6	37.60 ±0.35	2.40 ±0.09	42.40	1.480 ±.014	0.094 ±.004	1.668
2.40X039.6	39.60 ±0.35	2.40 ±0.09	44.40	1.559 ±.014	0.094 ±.004	1.747
2.40X041.6	41.60 ±0.35	2.40 ±0.09	46.40	1.638 ±.014	0.094 ±.004	1.826
2.40X044.6	44.60 ±0.35	2.40 ±0.09	49.40	1.756 ±.014	0.094 ±.004	1.944
2.40X045.6	45.60 ±0.35	2.40 ±0.09	50.40	1.795 ±.014	0.094 ±.004	1.983
2.40X047.6	47.60 ±0.35	2.40 ±0.09	52.40	1.874 ±.014	0.094 ±.004	2.062
2.40X049.6	49.60 ±0.35	2.40 ±0.09	54.40	1.953 ±.014	0.094 ±.004	2.141
2.40X051.6	51.60 ±0.40	2.40 ±0.09	56.40	2.031 ±.016	0.094 ±.004	2.220
2.40X054.6	54.60 ±0.40	2.40 ±0.09	59.40	2.150 ±.016	0.094 ±.004	2.338
2.40X055.6	55.60 ±0.40	2.40 ±0.09	60.40	2.189 ±.016	0.094 ±.004	2.377
2.40X057.6	57.60 ±0.40	2.40 ±0.09	62.40	2.268 ±.016	0.094 ±.004	2.456
2.40X058.6	58.60 ±0.40	2.40 ±0.09	63.40	2.307 ±.016	0.094 ±.004	2.495
2.40X059.6	59.60 ±0.40	2.40 ±0.09	64.40	2.346 ±.016	0.094 ±.004	2.534
2.40X061.6	61.60 ±0.40	2.40 ±0.09	66.40	2.425 ±.016	0.094 ±.004	2.613
2.40X062.6	62.60 ±0.40	2.40 ±0.09	67.40	2.465 ±.016	0.094 ±.004	2.653
2.40X064.6	64.60 ±0.40	2.40 ±0.09	69.40	2.543 ±.016	0.094 ±.004	2.731
2.40X067.6	67.60 ±0.40	2.40 ±0.09	72.40	2.661 ±.016	0.094 ±.004	2.849
2.40X069.6	69.60 ±0.40	2.40 ±0.09	74.40	2.740 ±.016	0.094 ±.004	2.928

3 mm cross-section

CS 3 mm · 58 sizes

BS 4518 3 mm cross-section size table
Code (CS×ID)	ID (mm)	CS (mm)	OD (mm)	ID (in)	CS (in)	OD (in)
3.00X019.5	19.50 ±0.25	3.00 ±0.09	25.50	0.768 ±.010	0.118 ±.004	1.004
3.00X021.5	21.50 ±0.25	3.00 ±0.09	27.50	0.847 ±.010	0.118 ±.004	1.083
3.00X022.5	22.50 ±0.25	3.00 ±0.09	28.50	0.886 ±.010	0.118 ±.004	1.122
3.00X024.5	24.50 ±0.25	3.00 ±0.09	30.50	0.965 ±.010	0.118 ±.004	1.201
3.00X025.5	25.50 ±0.25	3.00 ±0.09	31.50	1.004 ±.010	0.118 ±.004	1.240
3.00X026.5	26.50 ±0.25	3.00 ±0.09	32.50	1.043 ±.010	0.118 ±.004	1.279
3.00X027.5	27.50 ±0.25	3.00 ±0.09	33.50	1.083 ±.010	0.118 ±.004	1.319
3.00X029.5	29.50 ±0.25	3.00 ±0.09	35.50	1.161 ±.010	0.118 ±.004	1.397
3.00X031.5	31.50 ±0.35	3.00 ±0.09	37.50	1.240 ±.014	0.118 ±.004	1.476
3.00X032.5	32.50 ±0.35	3.00 ±0.09	38.50	1.280 ±.014	0.118 ±.004	1.516
3.00X034.5	34.50 ±0.35	3.00 ±0.09	40.50	1.358 ±.014	0.118 ±.004	1.594
3.00X035.5	35.50 ±0.35	3.00 ±0.09	41.50	1.398 ±.014	0.118 ±.004	1.634
3.00X036.5	36.50 ±0.35	3.00 ±0.09	42.50	1.437 ±.014	0.118 ±.004	1.673
3.00X037.5	37.50 ±0.35	3.00 ±0.09	43.50	1.476 ±.014	0.118 ±.004	1.712
3.00X039.5	39.50 ±0.35	3.00 ±0.09	45.50	1.555 ±.014	0.118 ±.004	1.791
3.00X041.5	41.50 ±0.35	3.00 ±0.09	47.50	1.634 ±.014	0.118 ±.004	1.870
3.00X042.5	42.50 ±0.35	3.00 ±0.09	48.50	1.673 ±.014	0.118 ±.004	1.909
3.00X044.5	44.50 ±0.35	3.00 ±0.09	50.50	1.752 ±.014	0.118 ±.004	1.988
3.00X049.5	49.50 ±0.35	3.00 ±0.09	55.50	1.949 ±.014	0.118 ±.004	2.185
3.00X054.5	54.50 ±0.40	3.00 ±0.09	60.50	2.146 ±.016	0.118 ±.004	2.382
3.00X055.5	55.50 ±0.40	3.00 ±0.09	61.50	2.185 ±.016	0.118 ±.004	2.421
3.00X057.5	57.50 ±0.40	3.00 ±0.09	63.50	2.264 ±.016	0.118 ±.004	2.500
3.00X059.5	59.50 ±0.40	3.00 ±0.09	65.50	2.342 ±.016	0.118 ±.004	2.579
3.00X062.5	62.50 ±0.40	3.00 ±0.09	68.50	2.461 ±.016	0.118 ±.004	2.697
3.00X064.5	64.50 ±0.40	3.00 ±0.09	70.50	2.539 ±.016	0.118 ±.004	2.775
3.00X069.5	69.50 ±0.40	3.00 ±0.09	75.50	2.736 ±.016	0.118 ±.004	2.972
3.00X074.5	74.50 ±0.40	3.00 ±0.09	80.50	2.933 ±.016	0.118 ±.004	3.169
3.00X079.5	79.50 ±0.40	3.00 ±0.09	85.50	3.130 ±.016	0.118 ±.004	3.366
3.00X084.5	84.50 ±0.50	3.00 ±0.09	90.50	3.327 ±.020	0.118 ±.004	3.563
3.00X089.5	89.50 ±0.50	3.00 ±0.09	95.50	3.524 ±.020	0.118 ±.004	3.760
3.00X094.5	94.50 ±0.50	3.00 ±0.09	100.50	3.720 ±.020	0.118 ±.004	3.957
3.00X099.5	99.50 ±0.50	3.00 ±0.09	105.50	3.917 ±.020	0.118 ±.004	4.153
3.00X104.5	104.50 ±0.50	3.00 ±0.09	110.50	4.114 ±.020	0.118 ±.004	4.350
3.00X109.5	109.50 ±0.50	3.00 ±0.09	115.50	4.311 ±.020	0.118 ±.004	4.547
3.00X114.5	114.50 ±0.50	3.00 ±0.09	120.50	4.508 ±.020	0.118 ±.004	4.744
3.00X119.5	119.50 ±0.50	3.00 ±0.09	125.50	4.705 ±.020	0.118 ±.004	4.941
3.00X124.5	124.50 ±0.70	3.00 ±0.09	130.50	4.902 ±.028	0.118 ±.004	5.138
3.00X129.5	129.50 ±0.70	3.00 ±0.09	135.50	5.098 ±.028	0.118 ±.004	5.334
3.00X134.5	134.50 ±0.70	3.00 ±0.09	140.50	5.295 ±.028	0.118 ±.004	5.531
3.00X139.5	139.50 ±0.70	3.00 ±0.09	145.50	5.492 ±.028	0.118 ±.004	5.728
3.00X144.5	144.50 ±0.70	3.00 ±0.09	150.50	5.689 ±.028	0.118 ±.004	5.925
3.00X149.5	149.50 ±0.70	3.00 ±0.09	155.50	5.886 ±.028	0.118 ±.004	6.122
3.00X154.5	154.50 ±0.70	3.00 ±0.09	160.50	6.083 ±.028	0.118 ±.004	6.319
3.00X159.5	159.50 ±0.70	3.00 ±0.09	165.50	6.279 ±.028	0.118 ±.004	6.515
3.00X164.5	164.50 ±0.70	3.00 ±0.09	170.50	6.476 ±.028	0.118 ±.004	6.712
3.00X169.5	169.50 ±0.70	3.00 ±0.09	175.50	6.673 ±.028	0.118 ±.004	6.909
3.00X174.5	174.50 ±0.70	3.00 ±0.09	180.50	6.870 ±.028	0.118 ±.004	7.106
3.00X179.5	179.50 ±0.70	3.00 ±0.09	185.50	7.067 ±.028	0.118 ±.004	7.303
3.00X184.5	184.50 ±0.90	3.00 ±0.09	190.50	7.264 ±.035	0.118 ±.004	7.500
3.00X189.5	189.50 ±0.90	3.00 ±0.09	195.50	7.461 ±.035	0.118 ±.004	7.697
3.00X194.5	194.50 ±0.90	3.00 ±0.09	200.50	7.657 ±.035	0.118 ±.004	7.893
3.00X199.5	199.50 ±0.90	3.00 ±0.09	205.50	7.854 ±.035	0.118 ±.004	8.090
3.00X209.5	209.50 ±0.90	3.00 ±0.09	215.50	8.248 ±.035	0.118 ±.004	8.484
3.00X219.5	219.50 ±0.90	3.00 ±0.09	225.50	8.642 ±.035	0.118 ±.004	8.878
3.00X229.5	229.50 ±0.90	3.00 ±0.09	235.50	9.035 ±.035	0.118 ±.004	9.271
3.00X239.5	239.50 ±0.90	3.00 ±0.09	245.50	9.429 ±.035	0.118 ±.004	9.665
3.00X244.5	244.50 ±0.90	3.00 ±0.09	250.50	9.626 ±.035	0.118 ±.004	9.862
3.00X249.5	249.50 ±0.90	3.00 ±0.09	255.50	9.823 ±.035	0.118 ±.004	10.059

5.7 mm cross-section

CS 5.7 mm · 59 sizes

BS 4518 5.7 mm cross-section size table
Code (CS×ID)	ID (mm)	CS (mm)	OD (mm)	ID (in)	CS (in)	OD (in)
5.70X044.3	44.30 ±0.35	5.70 ±0.13	55.70	1.744 ±.014	0.224 ±.005	2.192
5.70X045.3	45.30 ±0.35	5.70 ±0.13	56.70	1.784 ±.014	0.224 ±.005	2.232
5.70X049.3	49.30 ±0.35	5.70 ±0.13	60.70	1.941 ±.014	0.224 ±.005	2.389
5.70X052.3	52.30 ±0.40	5.70 ±0.13	63.70	2.059 ±.016	0.224 ±.005	2.507
5.70X054.3	54.30 ±0.40	5.70 ±0.13	65.70	2.138 ±.016	0.224 ±.005	2.586
5.70X055.3	55.30 ±0.40	5.70 ±0.13	66.70	2.177 ±.016	0.224 ±.005	2.625
5.70X059.3	59.30 ±0.40	5.70 ±0.13	70.70	2.335 ±.016	0.224 ±.005	2.783
5.70X062.3	62.30 ±0.40	5.70 ±0.13	73.70	2.453 ±.016	0.224 ±.005	2.901
5.70X064.3	64.30 ±0.40	5.70 ±0.13	75.70	2.531 ±.016	0.224 ±.005	2.979
5.70X069.3	69.30 ±0.40	5.70 ±0.13	80.70	2.728 ±.016	0.224 ±.005	3.176
5.70X074.3	74.30 ±0.40	5.70 ±0.13	85.70	2.925 ±.016	0.224 ±.005	3.373
5.70X079.3	79.30 ±0.40	5.70 ±0.13	90.70	3.122 ±.016	0.224 ±.005	3.570
5.70X084.3	84.30 ±0.50	5.70 ±0.13	95.70	3.319 ±.020	0.224 ±.005	3.767
5.70X089.3	89.30 ±0.50	5.70 ±0.13	100.70	3.516 ±.020	0.224 ±.005	3.964
5.70X094.3	94.30 ±0.50	5.70 ±0.13	105.70	3.713 ±.020	0.224 ±.005	4.161
5.70X099.3	99.30 ±0.50	5.70 ±0.13	110.70	3.909 ±.020	0.224 ±.005	4.357
5.70X104.3	104.30 ±0.50	5.70 ±0.13	115.70	4.106 ±.020	0.224 ±.005	4.554
5.70X109.3	109.30 ±0.50	5.70 ±0.13	120.70	4.303 ±.020	0.224 ±.005	4.751
5.70X114.3	114.30 ±0.50	5.70 ±0.13	125.70	4.500 ±.020	0.224 ±.005	4.948
5.70X119.3	119.30 ±0.50	5.70 ±0.13	130.70	4.697 ±.020	0.224 ±.005	5.145
5.70X124.3	124.30 ±0.70	5.70 ±0.13	135.70	4.894 ±.028	0.224 ±.005	5.342
5.70X129.3	129.30 ±0.70	5.70 ±0.13	140.70	5.091 ±.028	0.224 ±.005	5.539
5.70X134.3	134.30 ±0.70	5.70 ±0.13	145.70	5.287 ±.028	0.224 ±.005	5.735
5.70X139.3	139.30 ±0.70	5.70 ±0.13	150.70	5.484 ±.028	0.224 ±.005	5.932
5.70X144.3	144.30 ±0.70	5.70 ±0.13	155.70	5.681 ±.028	0.224 ±.005	6.129
5.70X149.3	149.30 ±0.70	5.70 ±0.13	160.70	5.878 ±.028	0.224 ±.005	6.326
5.70X154.3	154.30 ±0.70	5.70 ±0.13	165.70	6.075 ±.028	0.224 ±.005	6.523
5.70X159.3	159.30 ±0.70	5.70 ±0.13	170.70	6.272 ±.028	0.224 ±.005	6.720
5.70X164.3	164.30 ±0.70	5.70 ±0.13	175.70	6.468 ±.028	0.224 ±.005	6.917
5.70X169.3	169.30 ±0.70	5.70 ±0.13	180.70	6.665 ±.028	0.224 ±.005	7.113
5.70X174.3	174.30 ±0.70	5.70 ±0.13	185.70	6.862 ±.028	0.224 ±.005	7.310
5.70X179.3	179.30 ±0.70	5.70 ±0.13	190.70	7.059 ±.028	0.224 ±.005	7.507
5.70X184.3	184.30 ±0.90	5.70 ±0.13	195.70	7.256 ±.035	0.224 ±.005	7.704
5.70X189.3	189.30 ±0.90	5.70 ±0.13	200.70	7.453 ±.035	0.224 ±.005	7.901
5.70X194.3	194.30 ±0.90	5.70 ±0.13	205.70	7.650 ±.035	0.224 ±.005	8.098
5.70X199.3	199.30 ±0.90	5.70 ±0.13	210.70	7.846 ±.035	0.224 ±.005	8.294
5.70X209.3	209.30 ±0.90	5.70 ±0.13	220.70	8.240 ±.035	0.224 ±.005	8.688
5.70X219.3	219.30 ±0.90	5.70 ±0.13	230.70	8.634 ±.035	0.224 ±.005	9.082
5.70X229.3	229.30 ±0.90	5.70 ±0.13	240.70	9.028 ±.035	0.224 ±.005	9.476
5.70X239.3	239.30 ±0.90	5.70 ±0.13	250.70	9.421 ±.035	0.224 ±.005	9.869
5.70X249.3	249.30 ±0.90	5.70 ±0.13	260.70	9.815 ±.035	0.224 ±.005	10.263
5.70X259.3	259.30 ±1.20	5.70 ±0.13	270.70	10.209 ±.047	0.224 ±.005	10.657
5.70X269.3	269.30 ±1.20	5.70 ±0.13	280.70	10.602 ±.047	0.224 ±.005	11.050
5.70X279.3	279.30 ±1.20	5.70 ±0.13	290.70	10.996 ±.047	0.224 ±.005	11.444
5.70X289.3	289.30 ±1.20	5.70 ±0.13	300.70	11.390 ±.047	0.224 ±.005	11.838
5.70X299.3	299.30 ±1.20	5.70 ±0.13	310.70	11.784 ±.047	0.224 ±.005	12.232
5.70X309.3	309.30 ±1.20	5.70 ±0.13	320.70	12.177 ±.047	0.224 ±.005	12.625
5.70X319.3	319.30 ±1.20	5.70 ±0.13	330.70	12.571 ±.047	0.224 ±.005	13.019
5.70X339.3	339.30 ±1.20	5.70 ±0.13	350.70	13.358 ±.047	0.224 ±.005	13.806
5.70X359.3	359.30 ±1.20	5.70 ±0.13	370.70	14.146 ±.047	0.224 ±.005	14.594
5.70X379.3	379.30 ±1.20	5.70 ±0.13	390.70	14.933 ±.047	0.224 ±.005	15.381
5.70X389.3	389.30 ±1.20	5.70 ±0.13	400.70	15.327 ±.047	0.224 ±.005	15.775
5.70X399.3	399.30 ±1.20	5.70 ±0.13	410.70	15.720 ±.047	0.224 ±.005	16.168
5.70X419.3	419.30 ±1.20	5.70 ±0.13	430.70	16.508 ±.047	0.224 ±.005	16.956
5.70X439.3	439.30 ±1.20	5.70 ±0.13	450.70	17.295 ±.047	0.224 ±.005	17.743
5.70X459.3	459.30 ±1.20	5.70 ±0.13	470.70	18.083 ±.047	0.224 ±.005	18.531
5.70X479.3	479.30 ±1.20	5.70 ±0.13	490.70	18.870 ±.047	0.224 ±.005	19.318
5.70X489.3	489.30 ±1.20	5.70 ±0.13	500.70	19.264 ±.047	0.224 ±.005	19.712
5.70X499.3	499.30 ±1.20	5.70 ±0.13	510.70	19.657 ±.047	0.224 ±.005	20.105

8.4 mm cross-section

CS 8.4 mm · 19 sizes

BS 4518 8.4 mm cross-section size table
Code (CS×ID)	ID (mm)	CS (mm)	OD (mm)	ID (in)	CS (in)	OD (in)
8.40X144.1	144.10 ±0.70	8.40 ±0.18	160.90	5.673 ±.028	0.331 ±.007	6.335
8.40X149.1	149.10 ±0.70	8.40 ±0.18	165.90	5.870 ±.028	0.331 ±.007	6.532
8.40X154.1	154.10 ±0.70	8.40 ±0.18	170.90	6.067 ±.028	0.331 ±.007	6.729
8.40X159.1	159.10 ±0.70	8.40 ±0.18	175.90	6.264 ±.028	0.331 ±.007	6.926
8.40X164.1	164.10 ±0.70	8.40 ±0.18	180.90	6.461 ±.028	0.331 ±.007	7.123
8.40X169.1	169.10 ±0.70	8.40 ±0.18	185.90	6.657 ±.028	0.331 ±.007	7.319
8.40X174.1	174.10 ±0.70	8.40 ±0.18	190.90	6.854 ±.028	0.331 ±.007	7.516
8.40X179.1	179.10 ±0.70	8.40 ±0.18	195.90	7.051 ±.028	0.331 ±.007	7.713
8.40X184.1	184.10 ±0.90	8.40 ±0.18	200.90	7.248 ±.035	0.331 ±.007	7.910
8.40X189.1	189.10 ±0.90	8.40 ±0.18	205.90	7.445 ±.035	0.331 ±.007	8.107
8.40X194.1	194.10 ±0.90	8.40 ±0.18	210.90	7.642 ±.035	0.331 ±.007	8.304
8.40X199.1	199.10 ±0.90	8.40 ±0.18	215.90	7.839 ±.035	0.331 ±.007	8.501
8.40X204.1	204.10 ±0.90	8.40 ±0.18	220.90	8.035 ±.035	0.331 ±.007	8.697
8.40X209.1	209.10 ±0.90	8.40 ±0.18	225.90	8.232 ±.035	0.331 ±.007	8.894
8.40X219.1	219.10 ±0.90	8.40 ±0.18	235.90	8.626 ±.035	0.331 ±.007	9.288
8.40X229.1	229.10 ±0.90	8.40 ±0.18	245.90	9.020 ±.035	0.331 ±.007	9.682
8.40X234.1	234.10 ±0.90	8.40 ±0.18	250.90	9.216 ±.035	0.331 ±.007	9.879
8.40X239.1	239.10 ±0.90	8.40 ±0.18	255.90	9.413 ±.035	0.331 ±.007	10.075
8.40X249.1	249.10 ±0.90	8.40 ±0.18	265.90	9.807 ±.035	0.331 ±.007	10.469

Other size charts

Need	Chart
AS568 dash (0xx-4xx)	AS568 O-Ring Size Chart
Metric / ISO 3601	Metric O-Ring Size Chart
JIS S/P/G/V	JIS B 2401 Size Chart
ORB / 900-series boss	ORB Boss Size Chart
Back-up rings	Backup Ring Size Chart
DIN 3771	DIN 3771 Size Chart
Generic Metric	Generic Metric Size Chart
BS 4518	BS 4518 Size Chart
BS 1806	BS 1806 Size Chart
NF T 47-501	NF T 47-501 Size Chart
SMS 1586	SMS 1586 Size Chart
X-Ring	X-Ring Size Chart
Square Ring	Square Ring Size Chart
Parker 500	Parker 500 Size Chart
ISO 6149 ports	ISO 6149 Size Chart
Search across standards	Master O-Ring Size Chart

History and explanation of the BS 4518 standard

What BS 4518 is

BS 4518 covers metric O-Ring sizes used in UK and related markets. Callouts are millimeter based, not AS568-style dashes.

BS 4518 vs BS 1806

Standard	Style
BS 4518	Metric ID × CS
BS 1806	Imperial dash system closely aligned with AS568

If a British print still shows a three-digit dash like a US size, check BS 1806 / AS568. If it shows millimeters, use this page.

Using this chart

Match CS group, then ID. Confirm compound separately. Cross-check ISO if the drawing cites both British and international standards.

BS 4518 O-Ring Size Chart

1.6 mm cross-section

2.4 mm cross-section

3 mm cross-section

5.7 mm cross-section

8.4 mm cross-section

Other size charts

History and explanation of the BS 4518 standard

What BS 4518 is

BS 4518 vs BS 1806

Using this chart

Handbook

The O-Ring Store

Get In Touch

1.6 mm cross-section

2.4 mm cross-section

3 mm cross-section

5.7 mm cross-section

8.4 mm cross-section

Other size charts

Related

History and explanation of the BS 4518 standard

What BS 4518 is

BS 4518 vs BS 1806

Using this chart

Handbook

The O-Ring Store

Get In Touch