Technical Resource · Reference Only

BS 1806 O-Ring Size Chart

Complete BS 1806 dimensional reference — legacy British Standard inch-based O-ring sizes across all series, with metric equivalents. BS 1806 is withdrawn and replaced by BS ISO 3601-1; this chart is provided for cross-referencing older drawings.

BS 1806 was formally withdrawn and replaced by BS ISO 3601-1. This legacy reference is provided for cross-referencing older drawings and existing inventory. For new designs, use ISO 3601 or BS 4518 (metric).

Series 000

Cross-section 1/16″ (1.6 mm)

BS No.	ID (in)	OD (in)	CS (in)	ID (mm)	OD (mm)	CS (mm)
BS 003	0.056	0.176	0.060	1.42	4.47	1.52
BS 004	0.070	0.190	0.060	1.78	4.83	1.52
BS 005	0.101	0.221	0.060	2.57	5.61	1.52
BS 006	0.114	0.234	0.060	2.90	5.94	1.52
BS 007	0.171	0.291	0.060	4.34	7.39	1.52
BS 008	0.208	0.328	0.060	5.28	8.33	1.52
BS 009	0.239	0.359	0.060	6.07	9.12	1.52
BS 010	0.284	0.404	0.060	7.21	10.26	1.52
BS 011	0.351	0.471	0.060	8.92	11.96	1.52
BS 012	0.414	0.534	0.060	10.52	13.56	1.52
BS 013	0.468	0.588	0.060	11.89	14.94	1.52
BS 014	0.549	0.669	0.060	13.94	16.99	1.52

Series 100

Cross-section 3/32″ (2.6 mm)

BS No.	ID (in)	OD (in)	CS (in)	ID (mm)	OD (mm)	CS (mm)
BS 101	0.171	0.377	0.103	4.34	9.58	2.62
BS 102	0.208	0.414	0.103	5.28	10.52	2.62
BS 103	0.239	0.445	0.103	6.07	11.30	2.62
BS 104	0.284	0.490	0.103	7.21	12.45	2.62
BS 105	0.351	0.557	0.103	8.92	14.15	2.62
BS 106	0.414	0.620	0.103	10.52	15.75	2.62
BS 107	0.468	0.674	0.103	11.89	17.12	2.62
BS 108	0.549	0.755	0.103	13.94	19.18	2.62
BS 109	0.612	0.818	0.103	15.54	20.78	2.62
BS 110	0.674	0.880	0.103	17.12	22.35	2.62
BS 111	0.737	0.943	0.103	18.72	23.95	2.62
BS 112	0.799	1.005	0.103	20.29	25.53	2.62
BS 113	0.862	1.068	0.103	21.89	27.13	2.62
BS 114	0.924	1.130	0.103	23.47	28.70	2.62
BS 115	0.987	1.193	0.103	25.07	30.30	2.62
BS 116	1.049	1.255	0.103	26.64	31.88	2.62
BS 117	1.112	1.318	0.103	28.24	33.48	2.62
BS 118	1.174	1.380	0.103	29.82	35.05	2.62
BS 119	1.237	1.443	0.103	31.42	36.65	2.62
BS 120	1.299	1.505	0.103	32.99	38.23	2.62
BS 121	1.362	1.568	0.103	34.59	39.83	2.62
BS 122	1.424	1.630	0.103	36.17	41.40	2.62
BS 123	1.487	1.693	0.103	37.77	43.00	2.62
BS 124	1.549	1.755	0.103	39.34	44.58	2.62
BS 125	1.612	1.818	0.103	40.94	46.18	2.62
BS 126	1.674	1.880	0.103	42.52	47.75	2.62
BS 127	1.737	1.943	0.103	44.12	49.35	2.62
BS 128	1.799	2.005	0.103	45.69	50.93	2.62
BS 129	1.862	2.068	0.103	47.29	52.53	2.62
BS 130	1.924	2.130	0.103	48.87	54.10	2.62
BS 131	1.987	2.193	0.103	50.47	55.70	2.62

Series 200

Cross-section 1/8″ (3.5 mm)

BS No.	ID (in)	OD (in)	CS (in)	ID (mm)	OD (mm)	CS (mm)
BS 201	0.612	0.890	0.139	15.54	22.61	3.53
BS 202	0.674	0.952	0.139	17.12	24.18	3.53
BS 203	0.737	1.015	0.139	18.72	25.78	3.53
BS 204	0.799	1.077	0.139	20.29	27.36	3.53
BS 205	0.862	1.140	0.139	21.89	28.96	3.53
BS 206	0.924	1.202	0.139	23.47	30.53	3.53
BS 207	0.987	1.265	0.139	25.07	32.13	3.53
BS 208	1.049	1.327	0.139	26.64	33.71	3.53
BS 209	1.112	1.390	0.139	28.24	35.31	3.53
BS 210	1.174	1.452	0.139	29.82	36.88	3.53
BS 211	1.237	1.515	0.139	31.42	38.48	3.53
BS 212	1.299	1.577	0.139	32.99	40.06	3.53
BS 213	1.362	1.640	0.139	34.59	41.66	3.53
BS 214	1.424	1.702	0.139	36.17	43.23	3.53
BS 215	1.487	1.765	0.139	37.77	44.83	3.53
BS 216	1.549	1.827	0.139	39.34	46.41	3.53
BS 217	1.612	1.890	0.139	40.94	48.01	3.53
BS 218	1.674	1.952	0.139	42.52	49.58	3.53
BS 219	1.737	2.015	0.139	44.12	51.18	3.53
BS 220	1.799	2.077	0.139	45.69	52.76	3.53
BS 221	1.862	2.140	0.139	47.29	54.36	3.53
BS 222	1.924	2.202	0.139	48.87	55.93	3.53
BS 223	1.987	2.265	0.139	50.47	57.53	3.53
BS 224	2.087	2.365	0.139	53.01	60.07	3.53
BS 225	2.206	2.484	0.139	56.03	63.09	3.53
BS 226	2.337	2.615	0.139	59.36	66.42	3.53
BS 227	2.462	2.740	0.139	62.53	69.60	3.53
BS 228	2.587	2.865	0.139	65.71	72.77	3.53
BS 229	2.712	2.990	0.139	68.88	75.95	3.53
BS 230	2.837	3.115	0.139	72.06	79.12	3.53
BS 231	2.962	3.240	0.139	75.23	82.30	3.53
BS 232	3.087	3.365	0.139	78.41	85.47	3.53
BS 233	3.237	3.515	0.139	82.22	89.28	3.53
BS 234	3.362	3.640	0.139	85.39	92.46	3.53
BS 235	3.487	3.765	0.139	88.57	95.63	3.53
BS 236	3.612	3.890	0.139	91.74	98.81	3.53
BS 237	3.737	4.015	0.139	94.92	101.98	3.53
BS 238	3.862	4.140	0.139	98.09	105.16	3.53
BS 239	3.987	4.265	0.139	101.27	108.33	3.53
BS 240	4.112	4.390	0.139	104.44	111.51	3.53
BS 241	4.237	4.515	0.139	107.62	114.68	3.53
BS 242	4.362	4.640	0.139	110.79	117.86	3.53
BS 243	4.487	4.765	0.139	113.97	121.03	3.53
BS 244	4.612	4.890	0.139	117.14	124.21	3.53
BS 245	4.737	5.015	0.139	120.32	127.38	3.53
BS 246	4.862	5.140	0.139	123.49	130.56	3.53
BS 247	4.987	5.265	0.139	126.67	133.73	3.53

Series 300

Cross-section 3/16″ (5.3 mm)

BS No.	ID (in)	OD (in)	CS (in)	ID (mm)	OD (mm)	CS (mm)
BS 301	1.049	1.469	0.210	26.64	37.31	5.33
BS 302	1.174	1.594	0.210	29.82	40.49	5.33
BS 303	1.299	1.719	0.210	32.99	43.66	5.33
BS 304	1.424	1.844	0.210	36.17	46.84	5.33
BS 305	1.549	1.969	0.210	39.34	50.01	5.33
BS 306	1.674	2.094	0.210	42.52	53.19	5.33
BS 307	1.799	2.219	0.210	45.69	56.36	5.33
BS 308	1.924	2.344	0.210	48.87	59.54	5.33
BS 309	2.087	2.507	0.210	53.01	63.68	5.33
BS 310	2.337	2.757	0.210	59.36	70.03	5.33
BS 311	2.587	3.007	0.210	65.71	76.38	5.33
BS 312	2.837	3.257	0.210	72.06	82.73	5.33
BS 313	3.087	3.507	0.210	78.41	89.08	5.33
BS 314	3.362	3.782	0.210	85.39	96.06	5.33
BS 315	3.612	4.032	0.210	91.74	102.41	5.33
BS 316	3.862	4.282	0.210	98.09	108.76	5.33
BS 317	4.112	4.532	0.210	104.44	115.11	5.33
BS 318	4.362	4.782	0.210	110.79	121.46	5.33
BS 319	4.612	5.032	0.210	117.14	127.81	5.33
BS 320	4.862	5.282	0.210	123.49	134.16	5.33
BS 321	5.112	5.532	0.210	129.84	140.51	5.33
BS 322	5.362	5.782	0.210	136.19	146.86	5.33
BS 323	5.612	6.032	0.210	142.54	153.21	5.33
BS 324	5.862	6.282	0.210	148.89	159.56	5.33
BS 325	6.112	6.532	0.210	155.24	165.91	5.33
BS 326	6.362	6.782	0.210	161.59	172.26	5.33
BS 327	6.612	7.032	0.210	167.94	178.61	5.33
BS 328	6.862	7.282	0.210	174.29	184.96	5.33
BS 329	7.112	7.532	0.210	180.64	191.31	5.33
BS 330	7.362	7.782	0.210	186.99	197.66	5.33
BS 331	7.612	8.032	0.210	193.34	204.01	5.33
BS 332	7.862	8.282	0.210	199.69	210.36	5.33
BS 333	8.112	8.532	0.210	206.04	216.71	5.33
BS 334	8.362	8.782	0.210	212.39	223.06	5.33
BS 335	8.612	9.032	0.210	218.74	229.41	5.33
BS 336	8.862	9.282	0.210	225.09	235.76	5.33
BS 337	9.112	9.532	0.210	231.44	242.11	5.33
BS 338	9.362	9.782	0.210	237.79	248.46	5.33
BS 339	9.612	10.032	0.210	244.14	254.81	5.33
BS 340	9.862	10.282	0.210	250.49	261.16	5.33
BS 341	10.112	10.532	0.210	256.84	267.51	5.33
BS 342	10.612	11.032	0.210	269.54	280.21	5.33
BS 343	11.112	11.532	0.210	282.24	292.91	5.33
BS 344	11.612	12.032	0.210	294.94	305.61	5.33

Series 400

Cross-section 1/4″ (7.0 mm)

BS No.	ID (in)	OD (in)	CS (in)	ID (mm)	OD (mm)	CS (mm)
BS 401	2.337	2.887	0.275	59.36	73.33	6.99
BS 402	2.587	3.137	0.275	65.71	79.68	6.99
BS 403	2.837	3.387	0.275	72.06	86.03	6.99
BS 404	3.087	3.637	0.275	78.41	92.38	6.99
BS 405	3.362	3.912	0.275	85.39	99.36	6.99
BS 406	3.612	4.162	0.275	91.74	105.71	6.99
BS 407	3.862	4.412	0.275	98.09	112.06	6.99
BS 408	4.112	4.662	0.275	104.44	118.41	6.99
BS 409	4.362	4.912	0.275	110.79	124.76	6.99
BS 410	4.612	5.162	0.275	117.14	131.11	6.99
BS 411	4.862	5.412	0.275	123.49	137.46	6.99
BS 412	5.112	5.662	0.275	129.84	143.81	6.99
BS 413	5.362	5.912	0.275	136.19	150.16	6.99
BS 414	5.612	6.162	0.275	142.54	156.51	6.99
BS 415	5.862	6.412	0.275	148.89	162.86	6.99
BS 416	6.112	6.662	0.275	155.24	169.21	6.99
BS 417	6.362	6.912	0.275	161.59	175.56	6.99
BS 418	6.612	7.162	0.275	167.94	181.91	6.99
BS 419	6.862	7.412	0.275	174.29	188.26	6.99
BS 420	7.112	7.662	0.275	180.64	194.61	6.99
BS 421	7.612	8.162	0.275	193.34	207.31	6.99
BS 422	8.112	8.662	0.275	206.04	220.01	6.99
BS 423	8.612	9.162	0.275	218.74	232.71	6.99
BS 424	9.112	9.662	0.275	231.44	245.41	6.99
BS 425	9.612	10.162	0.275	244.14	258.11	6.99
BS 426	10.112	10.662	0.275	256.84	270.81	6.99
BS 427	10.612	11.162	0.275	269.54	283.51	6.99
BS 428	11.112	11.662	0.275	282.24	296.21	6.99
BS 429	11.612	12.162	0.275	294.94	308.91	6.99
BS 430	12.112	12.662	0.275	307.64	321.61	6.99
BS 431	12.612	13.162	0.275	320.34	334.31	6.99
BS 432	13.112	13.662	0.275	333.04	347.01	6.99
BS 433	13.612	14.162	0.275	345.74	359.71	6.99
BS 434	14.112	14.662	0.275	358.44	372.41	6.99
BS 435	14.612	15.162	0.275	371.14	385.11	6.99
BS 436	15.112	15.662	0.275	383.84	397.81	6.99
BS 437	15.612	16.162	0.275	396.54	410.51	6.99
BS 438	16.112	16.662	0.275	409.24	423.21	6.99
BS 439	16.612	17.162	0.275	421.94	435.91	6.99
BS 440	17.112	17.662	0.275	434.64	448.61	6.99
BS 441	17.612	18.162	0.275	447.34	461.31	6.99
BS 442	18.112	18.662	0.275	460.04	474.01	6.99
BS 443	18.612	19.162	0.275	472.74	486.71	6.99
BS 444	19.112	19.662	0.275	485.44	499.41	6.99
BS 445	19.612	20.162	0.275	498.14	512.11	6.99
BS 446	20.112	20.662	0.275	510.84	524.81	6.99
BS 447	21.112	21.662	0.275	536.24	550.21	6.99
BS 448	22.112	22.662	0.275	561.64	575.61	6.99
BS 449	23.112	23.662	0.275	587.04	601.01	6.99
BS 450	24.112	24.662	0.275	612.44	626.41	6.99
BS 451	25.112	25.662	0.275	637.84	651.81	6.99
BS 452	26.112	26.662	0.275	663.24	677.21	6.99

186 sizes listed across all series. BS 1806 is withdrawn — for new designs see ISO 3601. For sizes not listed, custom manufacturing is available.

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BS 1806 O-Ring Size Chart

Cross-section 1/16″ (1.6 mm)

Cross-section 3/32″ (2.6 mm)

Cross-section 1/8″ (3.5 mm)

Cross-section 3/16″ (5.3 mm)

Cross-section 1/4″ (7.0 mm)

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