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What are British Standard O-Ring sizes?

What are British Standard O-Ring sizes?

A common question is what are the sizing of various British Standard (BS) O-rings.

BS Numbers are a very common and easy way for identification but should you need to identify an o-ring by measuring then this conversion table below may be of assistance.

O-Ring Diagram

BS Number

O-Ring Size
(ID x Cross Section (mm))

Nominal Size (Inches)

ID	OD	Cross Section


BS001	0.74 x 1.02	1/32	3/32	1/32
BS002	1.07 x 1.27	3/64	9/64	3/64
BS003	1.42 x 1.52	1/16	3/16	1/16
BS004	1.78 x 1.78	5/64	13/64	1/16
BS005	2.57 x 1.78	3/32	7/32	1/16
BS006	2.90 x 1.78	1/8	1/4	1/16
BS007	3.68 x 1.78	5/32	9/32	1/16
BS008	4.47 x 1.78	3/16	5/16	1/16
BS009	5.28 x 1.78	7/32	11/32	1/16
BS010	6.07 x 1.78	1/4	3/8	1/16
BS011	7.65 x 1.78	5/16	7/16	1/16
BS012	9.25 x 1.78	3/8	1/2	1/16
BS013	10.82 x 1.78	7/16	9/16	1/16
BS014	12.42 x 1.78	1/2	5/8	1/16
BS015	14 x 1.78	9/16	11/16	1/16
BS016	15.6 x 1.78	5/8	3/4	1/16
BS017	17.17 x 1.78	11/16	13/16	1/16
BS018	18.77 x 1.78	3/4	7/8	1/16
BS019	20.35 x 1.78	13/16	15/16	1/16
BS020	21.95 x 1.78	7/8	1	1/16
BS021	23.52 x 1.78	15/16	1 1/16	1/16
BS022	25.12 x 1.78	1	1 1/8	1/16
BS023	26.7 x 1.78	1 1/16	1 3/16	1/16
BS024	28.3 x 1.78	1 1/8	1 1/4	1/16
BS025	29.87 x 1.78	1 13/16	1 5/16	1/16
BS026	31.47 x 1.78	1 1/4	1 3/8	1/16
BS027	33.05 x 1.78	1 5/16	1 7/16	1/16
BS028	34.65 x 1.78	1 3/8	1 1/2	1/16
BS029	37.82 x 1.78	1 1/2	1 5/8	1/16
BS030	41.0 x 1.78	1 5/8	1 3/4	1/16
BS031	44.17 x 1.78	1 3/4	1 7/8	1/16
BS032	47.35 x 1.78	1 7/8	2	1/16
BS033	50.52 x 1.78	2	2 1/8	1/16
BS034	53.7 x 1.78	2 1/8	2 1/4	1/16
BS035	56.87 x 1.78	2 1/4	2 3/8	1/16
BS036	60.05 x 1.78	2 3/8	2 1/2	1/16
BS037	63.22 x 1.781	2 1/2	2 5/8	1/16
BS038	66.4 x 1.78	2 5/8	2 3/4	1/16
BS039	69.57 x 1.78	2 3/4	2 7/8	1/16
BS040	72.75 x 1.78	2 7/8	3	1/16
BS041	75.92 x 1.78	3	3 1/8	1/16
BS042	82.27 x 1.78	3 1/4	3 3/8	1/16
BS043	88.62 x 1.78	3 1/2	3 5/8	1/16
BS044	94.97 x 1.78	3 3/4	3 7/8	1/16
BS045	101.32 x 1.78	4	4 1/8	1/16
BS046	107.67 x 1.78	4 1/4	4 3/8	1/16
BS047	114.02 x 1.78	4 1/2	4 5/8	1/16
BS048	120.37 x 1.78	4 3/4	4 7/8	1/16
BS049	126.72 x 1.78	5	5 1/8	1/16
BS050	133.07 x 1.78	5 1/4	5 3/8	1/16
BS102	1.25 x 2.62	1/16	1/4	3/32
BS103	2.06 x 2.62	3/32	9/32	3/32
BS104	2.85 x 2.62	1/8	5/16	3/32
BS105	3.63 x 2.62	5/32	11/32	3/32
BS106	4.42 x 2.62	3/16	3/8	3/32
BS107	5.23 x 2.62	7/32	13/32	3/32
BS108	6.02 x 2.62	1/4	7/16	3/32
BS109	7.60 x 2.62	5/16	1/2	3/32
BS110	9.20 x 2.62	3/8	9/16	3/32
BS111	10.77 x 2.62	7/16	5/8	3/32
BS112	12.37 x 2.62	1/2	11/16	3/32
BS113	13.95 x 2.62	9/16	3/4	3/32
BS114	15.55 x 2.62	5/8	13/16	3/32
BS115	17.12 x 2.62	11/16	7/8	3/32
BS116	18.72 x 2.62	3/4	15/16	3/32
BS117	20.30 x 2.62	13/16	1	3/32
BS118	21.90 x 2.62	7/8	1 1/16	3/32
BS119	23.47 x 2.62	15/16	1 1/8	3/32
BS120	25.07 x 2.62	1	1 3/16	3/32
BS121	26.65 x 2.62	1 1/16	1 1/4	3/32
BS122	28.25 x 2.62	1 1/8	1 5/16	3/32
BS123	29.82 x 2.62	1 13/16	1 3/8	3/32
BS124	31.42 x 2.62	1 1/4	1 7/16	3/32
BS125	33.0 x 2.62	1 5/16	1 1/2	3/32
BS126	34.6 x 2.62	1 3/8	1 9/16	3/32
BS127	36.17 x 2.62	1 7/16	1 5/8	3/32
BS128	37.77 x 2.62	1 1/2	1 11/16	3/32
BS129	39.35 x 2.62	1 9/16	1 3/4	3/32
BS130	40.95 x 2.62	1 5/8	1 5/8	3/32
BS131	42.52 x 2.62	1 11/16	1 3/4	3/32
BS132	44.12 x 2.62	1 3/4	1 15/16	3/32
BS133	45.7 x 2.62	1 13/16	2	3/32
BS134	47.30 x 2.62	1 7/8	2 1/16	3/32
BS135	48.90 x 2.62	1 15/16	2 1/8	3/32
BS136	50.47 x 2.62	2	2 3/16	3/32
BS137	52.07 x 2.62	2 1/16	2 1/4	3/32
BS138	53.64 x 2.62	2 1/8	2 5/16	3/32
BS139	55.25 x 2.62	2 3/16	2 3/8	3/32
BS140	56.82 x 2.62	2 1/4	2 7/16	3/32
BS141	58.42 x 2.62	2 5/16	2 1/2	3/32
BS142	59.99 x 2.62	2 3/8	2 9/16	3/32
BS143	61.60 x 2.62	2 7/16	2 5/8	3/32
BS144	63.17 x 2.62	2 1/2	2 11/16	3/32
BS145	64.77 x 2.62	2 9/16	2 3/4	3/32
BS146	66.34 x 2.62	2 5/8	2 13/16	3/32
BS147	67.95 x 2.62	2 11/16	2 7/8	3/32
BS148	69.52 x 2.62	2 3/4	2 15/16	3/32
BS149	71.12 x 2.62	2 13/16	3	3/32
BS150	72.70 x 2.62	2 7/8	3 1/16	3/32
BS151	75.87 x 2.62	3	3 3/16	3/32
BS152	82.22 x 2.62	3 1/4	3 7/16	3/32
BS153	88.57 x 2.62	3 1/2	3 11/16	3/32
BS154	94.92 x 2.62	3 3/4	3 15/16	3/32
BS155	101.27 x 2.62	4	4 3/16	3/32
BS156	107.62 x 2.62	4 1/4	4 7/16	3/32
BS157	113.97 x 2.62	4 1/2	4 11/16	3/32
BS158	120.32 x 2.62	4 3/4	4 15/16	3/32
BS159	126.67 x 2.62	5	5 3/16	3/32
BS160	133.02 x 2.62	5 1/4	5 7/16	3/32
BS161	139.37 x 2.62	5 1/2	5 11/16	3/32
BS162	145.72 x 2.62	5 3/4	5 15/16	3/32
BS163	152.07 x 2.62	6	6 3/16	3/32
BS164	158.42 x 2.62	6 1/4	6 7/16	3/32
BS165	164.77 x 2.62	6 1/2	6 11/16	3/32
BS166	171.12 x 2.62	6 3/4	6 15/16	3/32
BS167	177.47 x 2.62	7	7 3/16	3/32
BS168	183.82 x 2.62	7 1/4	7 7/16	3/32
BS169	190.17 x 2.62	7 1/2	7 11/16	3/32
BS170	196.52 x 2.62	7 3/4	7 15/16	3/32
BS171	202.87 x 2.62	8	8 3/16	3/32
BS172	209.22 x 2.62	8 1/4	8 7/16	3/32
BS173	215.57 x 2.62	8 1/2	8 11/16	3/32
BS174	221.92 x 2.62	8 3/4	8 15/16	3/32
BS175	228.27 x 2.62	9	9 3/16	3/32
BS176	234.62 x 2.62	9 1/4	9 7/16	3/32
BS177	240.97 x 2.62	9 1/2	9 11/16	3/32
BS178	247.32 x 2.62	9 3/4	9 15/16	3/32
BS201	4.34 x 3.53	3/16	7/16	1/8
BS202	5.94 x 3.53	1/4	1/2	1/8
BS203	7.52 x 3.53	5/16	9/16	1/8
BS204	9.12 x 3.53	3/8	5/8	1/8
BS205	10.69 x 3.53	7/16	11/16	1/8
BS206	12.29 x 3.53	1/2	3/4	1/8
BS207	13.87 x 3.53	9/16	13/16	1/8
BS208	15.47 x 3.53	5/8	7/8	1/8
BS209	17.04 x 3.53	11/16	15/16	1/8
BS210	18.64 x 3.53	3/4	1	1/8
BS211	20.22 x 3.53	13/16	1 1/16	1/8
BS212	21.82 x 3.53	7/8	1 1/8	1/8
BS213	23.39 x 3.53	15/16	1 3/16	1/8
BS214	24.99 x 3.53	1	1 1/4	1/8
BS215	26.57 x 3.53	1 1/16	1 5/16	1/8
BS216	28.17 x 3.53	1 1/8	1 3/8	1/8
BS217	29.74 x 3.53	1 13/16	1 7/16	1/8
BS218	31.34 x 3.53	1 1/4	1 1/2	1/8
BS219	32.92 x 3.53	1 5/16	1 9/16	1/8
BS220	34.52 x 3.53	1 3/8	1 5/8	1/8
BS221	36.09 x 3.53	1 7/16	1 11/16	1/8
BS222	37.69 x 3.53	1 1/2	1 3/4	1/8
BS223	40.87 x 3.53	1 5/8	1 7/8	1/8
BS224	44.09 x 3.53	1 3/4	2	1/8
BS225	47.22 x 3.53	1 7/8	2 1/8	1/8
BS226	50.39 x 3.53	2	2 1/4	1/8
BS227	53.57 x 3.53	2 1/8	2 3/8	1/8
BS228	56.75 x 3.53	2 1/4	2 1/2	1/8
BS229	59.92 x 3.53	2 3/8	2 5/8	1/8
BS230	63.09 x 3.53	2 1/2	2 3/4	1/8
BS231	66.27 x 3.53	2 5/8	2 7/8	1/8
BS232	69.44 x 3.53	2 3/4	3	1/8
BS233	72.62 x 3.53	2 7/8	3 1/8	1/8
BS234	75.80 x 3.53	3	3 1/4	1/8
BS235	78.97 x 3.53	3 1/8	3 3/8	1/8
BS236	82.14 x 3.53	3 1/4	3 1/2	1/8
BS237	85.32 x 3.53	3 3/8	3 5/8	1/8
BS238	88.49 x 3.53	3 1/2	3 3/4	1/8
BS239	91.67 x 3.53	3 5/8	3 7/8	1/8
BS240	94.84 x 3.53	3 3/4	4	1/8
BS241	98.02 x 3.53	3 7/8	4 1/8	1/8
BS242	101.20 x 3.53	4	4 1/4	1/8
BS243	104.37 x 3.53	4 1/8	4 3/8	1/8
BS244	107.54 x 3.53	4 1/4	4 1/2	1/8
BS245	110.72 x 3.53	4 3/8	4 5/8	1/8
BS246	113.89 x 3.53	4 1/2	4 3/4	1/8
BS247	117.07 x 3.53	4 5/8	4 7/8	1/8
BS248	120.24 x 3.53	4 3/4	5	1/8
BS249	123.42 x 3.53	4 7/8	5 1/8	1/8
BS250	126.60 x 3.53	5	5 1/4	1/8
BS251	129.77 x 3.53	5 1/8	5 3/8	1/8
BS252	132.95 x 3.53	5 1/4	5 1/2	1/8
BS253	136.12 x 3.53	5 3/8	5 5/8	1/8
BS254	139.30 x 3.53	5 1/2	5 3/4	1/8
BS255	142.47 x 3.53	5 5/8	5 7/8	1/8
BS256	145.64 x 3.53	5 3/4	6	1/8
BS257	148.82 x 3.53	5 7/8	6 1/8	1/8
BS258	152.0 x 3.53	6	6 1/4	1/8
BS259	158.34 x 3.53	6 1/4	6 1/2	1/8
BS260	164.70 x 3.53	6 1/2	6 3/4	1/8
BS261	171.04 x 3.53	6 3/4	7	1/8
BS262	177.40 x 3.53	7	7 1/4	1/8
BS263	183.74 x 3.53	7 1/4	7 1/2	1/8
BS264	190.10 x 3.53	7 1/2	7 3/4	1/8
BS265	196.44 x 3.53	7 3/4	8	1/8
BS266	202.80 x 3.53	8	7 1/4	1/8
BS267	209.14 x 3.53	8 1/4	7 1/2	1/8
BS268	215.50 x 3.53	8 1/2	7 3/4	1/8
BS269	221.84 x 3.53	8 3/4	9	1/8
BS270	228.20 x 3.53	9	7 1/4	1/8
BS271	234.55 x 3.53	9 1/4	7 1/2	1/8
BS272	240.90 x 3.53	9 1/2	7 3/4	1/8
BS273	247.25 x 3.53	9 3/4	10	1/8
BS274	253.60 x 3.53	10	10 1/4	1/8
BS275	266.29 x 3.53	10 1/2	10 3/4	1/8
BS276	278.99 x 3.53	11	11 1/4	1/8
BS277	291.69 x 3.53	11 1/2	11 3/4	1/8
BS278	304.39 x 3.53	12	12 1/4	1/8
BS279	329.79 x 3.53	13	13 1/4	1/8
BS280	355.19 x 3.53	14	14 1/4	1/8
BS281	380.59 x 3.53	15	15 1/4	1/8
BS282	405.26 x 3.53	16	16 1/4	1/8
BS283	430.66 x 3.53	17	17 1/4	1/8
BS284	456.06 x 3.53	18	18 1/4	1/8
BS309	10.47 x 5.33	7/16	7/16	3/16
BS310	12.07 x 5.33	1/2	1/2	3/16
BS311	13.64 x 5.33	9/16	9/16	3/16
BS312	15.24 x 5.33	5/8	5/8	3/16
BS313	16.82 x 5.33	11/16	11/16	3/16
BS314	18.42 x 5.33	3/4	3/4	3/16
BS315	19.99 x 5.33	13/16	13/16	3/16
BS316	21.59 x 5.33	7/8	7/8	3/16
BS317	23.17 x 5.33	15/16	15/16	3/16
BS318	24.77 x 5.33	1	1	3/16
BS319	26.34 x 5.33	1 1/16	1 1/16	3/16
BS320	27.94 x 5.33	1 1/8	1 1/8	3/16
BS321	29.52 x 5.33	1 13/16	1 3/16	3/16
BS322	31.12 x 5.33	1 1/4	1 5/8	3/16
BS323	32.69 x 5.33	1 5/16	1 11/16	3/16
BS324	34.29 x 5.33	1 3/8	1 3/4	3/16
BS325	37.47 x 5.33	1 1/2	1 7/8	3/16
BS326	40.64 x 5.33	1 5/8	2	3/16
BS327	43.82 x 5.33	1 3/4	2 1/8	3/16
BS328	46.99 x 5.33	1 7/8	2 1/4	3/16
BS329	50.17 x 5.33	2	2 3/8	3/16
BS330	53.34 x 5.33	2 1/8	2 1/2	3/16
BS331	56.52 x 5.33	2 1/4	2 5/8	3/16
BS332	59.69 x 5.33	2 3/8	2 3/4	3/16
BS333	62.87 x 5.33	2 1/2	2 7/8	3/16
BS334	66.64 x 5.33	2 5/8	3	3/16
BS335	69.22 x 5.33	2 3/4	3 1/8	3/16
BS336	72.39 x 5.33	2 7/8	3 1/4	3/16
BS337	75.57 x 5.33	3	3 3/8	3/16
BS338	78.74 x 5.33	3 1/8	3 1/2	3/16
BS339	81.92 x 5.33	3 1/4	3 5/8	3/16
BS340	85.09 x 5.33	3 3/8	3 3/4	3/16
BS341	88.27 x 5.33	3 1/2	3 7/8	3/16
BS342	91.44 x 5.33	3 5/8	4	3/16
BS343	94.62 x 5.33	3 3/4	4 1/8	3/16
BS344	97.79 x 5.33	3 7/8	4 1/4	3/16
BS345	100.97 x 5.33	4	4 3/8	3/16
BS346	104.14 x 5.33	4 1/8	4 1/2	3/16
BS347	107.32 x 5.33	4 1/4	4 5/8	3/16
BS348	110.49 x 5.33	4 3/8	4 3/4	3/16
BS349	113.67 x 5.33	4 1/2	4 7/8	3/16
BS350	116.84 x 5.33	4 5/8	5	3/16
BS351	120.02 x 5.33	4 3/4	5 1/8	3/16
BS352	123.19 x 5.33	4 7/8	5 1/4	3/16
BS353	126.37 x 5.33	5	5 3/8	3/16
BS354	129.54 x 5.33	5 1/8	5 1/2	3/16
BS355	132.72 x 5.33	5 1/4	5 5/8	3/16
BS356	135.89 x 5.33	5 3/8	5 3/4	3/16
BS357	139.07 x 5.33	5 1/2	5 7/8	3/16
BS358	142.24 x 5.33	5 5/8	6	3/16
BS359	145.42 x 5.33	5 3/4	6 1/8	3/16
BS360	148.59 x 5.33	5 7/8	6 1/4	3/16
BS361	151.77 x 5.33	6	6 3/8	3/16
BS362	158.12 x 5.33	6 1/4	6 5/8	3/16
BS363	164.47 x 5.33	6 1/2	6 7/8	3/16
BS364	170.82 x 5.33	4 3/4	7 1/8	3/16
BS365	177.17 x 5.33	7	7 3/8	3/16
BS366	183.52 x 5.33	7 1/4	7 5/8	3/16
BS367	189.87 x 5.33	7 1/2	7 7/8	3/16
BS368	196.22 x 5.33	7 3/4	8 1/8	3/16
BS369	202.57 x 5.33	8	8 3/8	3/16
BS370	208.92 x 5.33	8 1/4	8 5/8	3/16
BS371	215.27 x 5.33	8 1/2	8 7/8	3/16
BS372	221.62 x 5.33	8 3/4	9 1/8	3/16
BS373	227.97 x 5.33	9	9 3/8	3/16
BS374	234.32 x 5.33	9 1/4	9 5/8	3/16
BS375	240.67 x 5.33	9 1/2	9 7/8	3/16
BS376	247.02 x 5.33	9 3/4	10 1/8	3/16
BS377	253.37 x 5.33	10	10 3/8	3/16
BS378	266.07 x 5.33	10 1/2	10 7/8	3/16
BS379	278.77 x 5.33	11	11 3/8	3/16
BS380	291.47 x 5.33	11 1/2	11 7/8	3/16
BS381	304.17 x 5.33	12	12 3/8	3/16
BS382	329.57 x 5.33	13	13 3/8	3/16
BS383	354.97 x 5.33	14	14 3/8	3/16
BS384	380.37 x 5.33	15	15 3/8	3/16
BS385	405.26 x 5.33	16	16 3/8	3/16
BS386	430.66 x 5.33	17	17 3/8	3/16
BS387	456.06 x 5.33	18	18 3/8	3/16
BS388	481.38 x 5.33	19	19 3/8	3/16
BS389	506.78 x 5.33	20	20 3/8	3/16
BS390	532.18 x 5.33	21	21 3/8	3/16
BS391	557.58 x 5.33	22	22 3/8	3/16
BS392	582.68 x 5.33	23	23 3/8	3/16
BS393	608.08 x 5.33	24	24 3/8	3/16
BS394	633.48 x 5.33	25	25 3/8	3/16
BS395	658.88 x 5.33	26	26 3/8	3/16
BS425	113.67 x 7	4 1/2	5	1/4
BS426	116.84 x 7	4 5/8	5 1/8	1/4
BS427	120.02 x 7	4 3/4	5 1/4	1/4
BS428	123.19 x 7	4 7/8	5 3/8	1/4
BS429	126.37 x 7	5	5 1/2	1/4
BS430	129.54 x 7	5 1/8	5 5/8	1/4
BS431	132.72 x 7	5 1/4	5 3/4	1/4
BS432	135.89 x 7	5 3/8	5 7/8	1/4
BS433	139.07 x 7	5 1/2	6	1/4
BS434	142.24 x 7	5 5/8	6 1/8	1/4
BS435	145.42 x 7	5 3/4	6 1/4	1/4
BS436	148.59 x 7	5 7/8	6 3/8	1/4
BS437	151.77 x 7	6	6 1/2	1/4
BS438	158.12 x 7	6 1/4	6 3/4	1/4
BS439	164.47 x 7	6 1/2	7	1/4
BS440	170.82 x 7	4 3/4	7 1/4	1/4
BS441	177.17 x 7	7	7 1/2	1/4
BS442	183.52 x 7	7 1/4	7 3/4	1/4
BS443	189.87 x 7	7 1/2	8	1/4
BS444	196.22 x 7	7 3/4	8 1/4	1/4
BS445	202.57 x 7	8	8 1/2	1/4
BS446	215.27 x 7	8 1/2	9	1/4
BS447	227.97 x 7	9	9 1/2	1/4
BS448	240.67 x 7	9 1/2	10	1/4
BS449	253.37 x 7	10	10 1/2	1/4
BS450	266.07 x 7	10 1/2	11	1/4
BS451	278..77 x 7	11	11 1/2	1/4
BS452	291.47 x 7	11 1/2	12	1/4
BS453	304.17 x 7	12	12 1/2	1/4
BS454	316.87 x 7	12 1/2	13	1/4
BS455	329.57 x 7	13	13 1/2	1/4
BS456	342.27 x 7	13 1/2	14	1/4
BS457	354.97 x 7	14	14 1/2	1/4
BS458	367.67 x 7	14 1/2	15	1/4
BS459	380.37 x 7	15	15 1/2	1/4
BS460	393.07 x 7	15 1/2	16	1/4
BS461	405.26 x 7	16	16 1/2	1/4
BS462	417.96 x 7	16 1/2	17	1/4
BS463	430.66 x 7	17	17 1/2	1/4
BS464	443.36 x 7	17 1/2	18	1/4
BS465	456.06 x 7	18	18 1/2	1/4
BS466	468.76 x 7	18 1/2	19	1/4
BS467	481.46 x 7	19	19 1/2	1/4
BS468	494.16 x 7	19 1/2	20	1/4
BS469	506.86 x 7	20	20 1/2	1/4
BS470	532.26 x 7	21	21 1/2	1/4
BS471	557.66 x 7	22	22 1/2	1/4
BS472	582.68 x 7	23	23 1/2	1/4
BS473	608.08 x 7	24	24 1/2	1/4
BS474	633.48 x 7	25	25 1/2	1/4
BS475	658.88 x 7	26	26 1/2	1/4
BS901	4.7 x 1.42
BS902	6.02 x 1.63
BS903	7.65 x 1.63
BS904	8.92 x 1.83
BS905	10.72 x 1.83
BS906	11.90 x 1.98
BS907	13.46 x 2.08
BS908	16.36 x 2.21
BS909	17.93 x 2.46
BS910	19.18 x 2.46
BS911	21.92 x 2.95
BS912	23.47 x 2.95
BS913	25.04 x 2.95
BS914	26.61 x 2.95
BS916	29.74 x 2.95
BS918	34.42 x 2.95
BS920	37.47 x 3
BS924	43.69 x 3.00
BS928	53.09 x 3.00
BS932	59.36 x 3.00