O-Ring Size Chart: AS568 Dash Numbers, ID, OD, CS

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AS568 dash number Used with: Dimensions from an AS568 dash number

Inside diameter Used with: Dash number from measured dimensions

Cross-section (cord thickness) Used with: Dash number from measured dimensions

Unit of the measurements Used with: Dash number from measured dimensions

Worked example

These are example values. Change any entry above and press Calculate to run your own numbers.

AS568 dash number	-210
Inside diameter (ID)	0.734 in (18.64 mm)
Cross-section (CS)	0.139 in (3.53 mm)
Outside diameter (OD)	1.012 in (25.7 mm) OD = ID + 2 × CS

Dimensions are nominal: each size has a tolerance that grows with the diameter, so see the maker's data for the limits. Inside diameter and cross-section are what identify the ring; the material and hardness are specified separately.

How it works

An AS568 dash number identifies a standard O-ring by its inside diameter and its cross-section, the thickness of the cord. The first digit of the three-digit number tells you the cross-section series: the 100 series is 0.103 inch (2.62 mm), the 200 series 0.139 inch (3.53 mm), the 300 series 0.210 inch (5.33 mm) and the 400 series 0.275 inch (6.99 mm). Sizes in the 0 series, from -001 to -050, are mostly 0.070 inch (1.78 mm).

The formulas

Outside diameter = inside diameter + 2 × cross-section
Cross-section by series: 0 series 0.070 in (-004 to -050), 100 series 0.103 in, 200 series 0.139 in, 300 series 0.210 in, 400 series 0.275 in
1 inch = 25.4 mm

Reference tables

AS568 0 series (cross-sections 0.040 to 0.070 in)

Dash	ID (in)	CS (in)	OD (in)	ID (mm)	CS (mm)	OD (mm)
-001	0.029	0.04	0.109	0.7366	1.02	2.769
-002	0.042	0.05	0.142	1.067	1.27	3.607
-003	0.056	0.06	0.176	1.422	1.52	4.47
-004	0.07	0.07	0.21	1.778	1.78	5.334
-005	0.101	0.07	0.241	2.565	1.78	6.121
-006	0.114	0.07	0.254	2.896	1.78	6.452
-007	0.145	0.07	0.285	3.683	1.78	7.239
-008	0.176	0.07	0.316	4.47	1.78	8.026
-009	0.208	0.07	0.348	5.283	1.78	8.839
-010	0.239	0.07	0.379	6.071	1.78	9.627
-011	0.301	0.07	0.441	7.645	1.78	11.2
-012	0.364	0.07	0.504	9.246	1.78	12.8
-013	0.426	0.07	0.566	10.82	1.78	14.38
-014	0.489	0.07	0.629	12.42	1.78	15.98
-015	0.551	0.07	0.691	14	1.78	17.55
-016	0.614	0.07	0.754	15.6	1.78	19.15
-017	0.676	0.07	0.816	17.17	1.78	20.73
-018	0.739	0.07	0.879	18.77	1.78	22.33
-019	0.801	0.07	0.941	20.35	1.78	23.9
-020	0.864	0.07	1.004	21.95	1.78	25.5
-021	0.926	0.07	1.066	23.52	1.78	27.08
-022	0.989	0.07	1.129	25.12	1.78	28.68
-023	1.051	0.07	1.191	26.7	1.78	30.25
-024	1.114	0.07	1.254	28.3	1.78	31.85
-025	1.176	0.07	1.316	29.87	1.78	33.43
-026	1.239	0.07	1.379	31.47	1.78	35.03
-027	1.301	0.07	1.441	33.05	1.78	36.6
-028	1.364	0.07	1.504	34.65	1.78	38.2
-029	1.489	0.07	1.629	37.82	1.78	41.38
-030	1.614	0.07	1.754	41	1.78	44.55
-031	1.739	0.07	1.879	44.17	1.78	47.73
-032	1.864	0.07	2.004	47.35	1.78	50.9
-033	1.989	0.07	2.129	50.52	1.78	54.08
-034	2.114	0.07	2.254	53.7	1.78	57.25
-035	2.239	0.07	2.379	56.87	1.78	60.43
-036	2.364	0.07	2.504	60.05	1.78	63.6
-037	2.489	0.07	2.629	63.22	1.78	66.78
-038	2.614	0.07	2.754	66.4	1.78	69.95
-039	2.739	0.07	2.879	69.57	1.78	73.13
-040	2.864	0.07	3.004	72.75	1.78	76.3
-041	2.989	0.07	3.129	75.92	1.78	79.48
-042	3.239	0.07	3.379	82.27	1.78	85.83
-043	3.489	0.07	3.629	88.62	1.78	92.18
-044	3.739	0.07	3.879	94.97	1.78	98.53
-045	3.989	0.07	4.129	101.3	1.78	104.9
-046	4.239	0.07	4.379	107.7	1.78	111.2
-047	4.489	0.07	4.629	114	1.78	117.6
-048	4.739	0.07	4.879	120.4	1.78	123.9
-049	4.989	0.07	5.129	126.7	1.78	130.3
-050	5.239	0.07	5.379	133.1	1.78	136.6

AS568 100 series (0.103 in cross-section)

Dash	ID (in)	CS (in)	OD (in)	ID (mm)	CS (mm)	OD (mm)
-102	0.049	0.103	0.255	1.245	2.62	6.477
-103	0.081	0.103	0.287	2.057	2.62	7.29
-104	0.112	0.103	0.318	2.845	2.62	8.077
-105	0.143	0.103	0.349	3.632	2.62	8.865
-106	0.174	0.103	0.38	4.42	2.62	9.652
-107	0.206	0.103	0.412	5.232	2.62	10.46
-108	0.237	0.103	0.443	6.02	2.62	11.25
-109	0.299	0.103	0.505	7.595	2.62	12.83
-110	0.362	0.103	0.568	9.195	2.62	14.43
-111	0.424	0.103	0.63	10.77	2.62	16
-112	0.487	0.103	0.693	12.37	2.62	17.6
-113	0.549	0.103	0.755	13.94	2.62	19.18
-114	0.612	0.103	0.818	15.54	2.62	20.78
-115	0.674	0.103	0.88	17.12	2.62	22.35
-116	0.737	0.103	0.943	18.72	2.62	23.95
-117	0.799	0.103	1.005	20.29	2.62	25.53
-118	0.862	0.103	1.068	21.89	2.62	27.13
-119	0.924	0.103	1.13	23.47	2.62	28.7
-120	0.987	0.103	1.193	25.07	2.62	30.3
-121	1.049	0.103	1.255	26.64	2.62	31.88
-122	1.112	0.103	1.318	28.24	2.62	33.48
-123	1.174	0.103	1.38	29.82	2.62	35.05
-124	1.237	0.103	1.443	31.42	2.62	36.65
-125	1.299	0.103	1.505	32.99	2.62	38.23
-126	1.362	0.103	1.568	34.59	2.62	39.83
-127	1.424	0.103	1.63	36.17	2.62	41.4
-128	1.487	0.103	1.693	37.77	2.62	43
-129	1.549	0.103	1.755	39.34	2.62	44.58
-130	1.612	0.103	1.818	40.94	2.62	46.18
-131	1.674	0.103	1.88	42.52	2.62	47.75
-132	1.737	0.103	1.943	44.12	2.62	49.35
-133	1.799	0.103	2.005	45.69	2.62	50.93
-134	1.862	0.103	2.068	47.29	2.62	52.53
-135	1.925	0.103	2.131	48.89	2.62	54.13
-136	1.987	0.103	2.193	50.47	2.62	55.7
-137	2.05	0.103	2.256	52.07	2.62	57.3
-138	2.112	0.103	2.318	53.64	2.62	58.88
-139	2.175	0.103	2.381	55.24	2.62	60.48
-140	2.237	0.103	2.443	56.82	2.62	62.05
-141	2.3	0.103	2.506	58.42	2.62	63.65
-142	2.362	0.103	2.568	59.99	2.62	65.23
-143	2.425	0.103	2.631	61.59	2.62	66.83
-144	2.487	0.103	2.693	63.17	2.62	68.4
-145	2.55	0.103	2.756	64.77	2.62	70
-146	2.612	0.103	2.818	66.34	2.62	71.58
-147	2.675	0.103	2.881	67.95	2.62	73.18
-148	2.737	0.103	2.943	69.52	2.62	74.75
-149	2.8	0.103	3.006	71.12	2.62	76.35
-150	2.862	0.103	3.068	72.69	2.62	77.93
-151	2.987	0.103	3.193	75.87	2.62	81.1
-152	3.237	0.103	3.443	82.22	2.62	87.45
-153	3.487	0.103	3.693	88.57	2.62	93.8
-154	3.737	0.103	3.943	94.92	2.62	100.2
-155	3.987	0.103	4.193	101.3	2.62	106.5
-156	4.237	0.103	4.443	107.6	2.62	112.9
-157	4.487	0.103	4.693	114	2.62	119.2
-158	4.737	0.103	4.943	120.3	2.62	125.6
-159	4.987	0.103	5.193	126.7	2.62	131.9
-160	5.237	0.103	5.443	133	2.62	138.3
-161	5.487	0.103	5.693	139.4	2.62	144.6
-162	5.737	0.103	5.943	145.7	2.62	151
-163	5.987	0.103	6.193	152.1	2.62	157.3
-164	6.237	0.103	6.443	158.4	2.62	163.7
-165	6.487	0.103	6.693	164.8	2.62	170
-166	6.737	0.103	6.943	171.1	2.62	176.4
-167	6.987	0.103	7.193	177.5	2.62	182.7
-168	7.237	0.103	7.443	183.8	2.62	189.1
-169	7.487	0.103	7.693	190.2	2.62	195.4
-170	7.737	0.103	7.943	196.5	2.62	201.8
-171	7.987	0.103	8.193	202.9	2.62	208.1
-172	8.237	0.103	8.443	209.2	2.62	214.5
-173	8.487	0.103	8.693	215.6	2.62	220.8
-174	8.737	0.103	8.943	221.9	2.62	227.2
-175	8.987	0.103	9.193	228.3	2.62	233.5
-176	9.237	0.103	9.443	234.6	2.62	239.9
-177	9.487	0.103	9.693	241	2.62	246.2
-178	9.737	0.103	9.943	247.3	2.62	252.6

AS568 200 series (0.139 in cross-section)

Dash	ID (in)	CS (in)	OD (in)	ID (mm)	CS (mm)	OD (mm)
-201	0.171	0.139	0.449	4.343	3.53	11.4
-202	0.234	0.139	0.512	5.944	3.53	13
-203	0.296	0.139	0.574	7.518	3.53	14.58
-204	0.359	0.139	0.637	9.119	3.53	16.18
-205	0.421	0.139	0.699	10.69	3.53	17.75
-206	0.484	0.139	0.762	12.29	3.53	19.35
-207	0.546	0.139	0.824	13.87	3.53	20.93
-208	0.609	0.139	0.887	15.47	3.53	22.53
-209	0.671	0.139	0.949	17.04	3.53	24.1
-210	0.734	0.139	1.012	18.64	3.53	25.7
-211	0.796	0.139	1.074	20.22	3.53	27.28
-212	0.859	0.139	1.137	21.82	3.53	28.88
-213	0.921	0.139	1.199	23.39	3.53	30.45
-214	0.984	0.139	1.262	24.99	3.53	32.05
-215	1.046	0.139	1.324	26.57	3.53	33.63
-216	1.109	0.139	1.387	28.17	3.53	35.23
-217	1.171	0.139	1.449	29.74	3.53	36.8
-218	1.234	0.139	1.512	31.34	3.53	38.4
-219	1.296	0.139	1.574	32.92	3.53	39.98
-220	1.359	0.139	1.637	34.52	3.53	41.58
-221	1.421	0.139	1.699	36.09	3.53	43.15
-222	1.484	0.139	1.762	37.69	3.53	44.75
-223	1.609	0.139	1.887	40.87	3.53	47.93
-224	1.734	0.139	2.012	44.04	3.53	51.1
-225	1.859	0.139	2.137	47.22	3.53	54.28
-226	1.984	0.139	2.262	50.39	3.53	57.45
-227	2.109	0.139	2.387	53.57	3.53	60.63
-228	2.234	0.139	2.512	56.74	3.53	63.8
-229	2.359	0.139	2.637	59.92	3.53	66.98
-230	2.484	0.139	2.762	63.09	3.53	70.15
-231	2.609	0.139	2.887	66.27	3.53	73.33
-232	2.734	0.139	3.012	69.44	3.53	76.5
-233	2.859	0.139	3.137	72.62	3.53	79.68
-234	2.984	0.139	3.262	75.79	3.53	82.85
-235	3.109	0.139	3.387	78.97	3.53	86.03
-236	3.234	0.139	3.512	82.14	3.53	89.2
-237	3.359	0.139	3.637	85.32	3.53	92.38
-238	3.484	0.139	3.762	88.49	3.53	95.55
-239	3.609	0.139	3.887	91.67	3.53	98.73
-240	3.734	0.139	4.012	94.84	3.53	101.9
-241	3.859	0.139	4.137	98.02	3.53	105.1
-242	3.984	0.139	4.262	101.2	3.53	108.3
-243	4.109	0.139	4.387	104.4	3.53	111.4
-244	4.234	0.139	4.512	107.5	3.53	114.6
-245	4.359	0.139	4.637	110.7	3.53	117.8
-246	4.484	0.139	4.762	113.9	3.53	121
-247	4.609	0.139	4.887	117.1	3.53	124.1
-248	4.734	0.139	5.012	120.2	3.53	127.3
-249	4.859	0.139	5.137	123.4	3.53	130.5
-250	4.984	0.139	5.262	126.6	3.53	133.7
-251	5.109	0.139	5.387	129.8	3.53	136.8
-252	5.234	0.139	5.512	132.9	3.53	140
-253	5.359	0.139	5.637	136.1	3.53	143.2
-254	5.484	0.139	5.762	139.3	3.53	146.4
-255	5.609	0.139	5.887	142.5	3.53	149.5
-256	5.734	0.139	6.012	145.6	3.53	152.7
-257	5.859	0.139	6.137	148.8	3.53	155.9
-258	5.984	0.139	6.262	152	3.53	159.1
-259	6.234	0.139	6.512	158.3	3.53	165.4
-260	6.484	0.139	6.762	164.7	3.53	171.8
-261	6.734	0.139	7.012	171	3.53	178.1
-262	6.984	0.139	7.262	177.4	3.53	184.5
-263	7.234	0.139	7.512	183.7	3.53	190.8
-264	7.484	0.139	7.762	190.1	3.53	197.2
-265	7.734	0.139	8.012	196.4	3.53	203.5
-266	7.984	0.139	8.262	202.8	3.53	209.9
-267	8.234	0.139	8.512	209.1	3.53	216.2
-268	8.484	0.139	8.762	215.5	3.53	222.6
-269	8.734	0.139	9.012	221.8	3.53	228.9
-270	8.984	0.139	9.262	228.2	3.53	235.3
-271	9.234	0.139	9.512	234.5	3.53	241.6
-272	9.484	0.139	9.762	240.9	3.53	248
-273	9.734	0.139	10.01	247.2	3.53	254.3
-274	9.984	0.139	10.26	253.6	3.53	260.7
-275	10.48	0.139	10.76	266.3	3.53	273.4
-276	10.98	0.139	11.26	279	3.53	286.1
-277	11.48	0.139	11.76	291.7	3.53	298.8
-278	11.98	0.139	12.26	304.4	3.53	311.5
-279	12.98	0.139	13.26	329.8	3.53	336.9
-280	13.98	0.139	14.26	355.2	3.53	362.3
-281	14.98	0.139	15.26	380.6	3.53	387.7
-282	15.96	0.139	16.23	405.3	3.53	412.3
-283	16.96	0.139	17.23	430.7	3.53	437.7
-284	17.96	0.139	18.23	456.1	3.53	463.1

AS568 300 series (0.210 in cross-section)

Dash	ID (in)	CS (in)	OD (in)	ID (mm)	CS (mm)	OD (mm)
-309	0.412	0.21	0.832	10.46	5.33	21.13
-310	0.475	0.21	0.895	12.07	5.33	22.73
-311	0.537	0.21	0.957	13.64	5.33	24.31
-312	0.6	0.21	1.02	15.24	5.33	25.91
-313	0.662	0.21	1.082	16.81	5.33	27.48
-314	0.725	0.21	1.145	18.42	5.33	29.08
-315	0.787	0.21	1.207	19.99	5.33	30.66
-316	0.85	0.21	1.27	21.59	5.33	32.26
-317	0.912	0.21	1.332	23.16	5.33	33.83
-318	0.975	0.21	1.395	24.76	5.33	35.43
-319	1.037	0.21	1.457	26.34	5.33	37.01
-320	1.1	0.21	1.52	27.94	5.33	38.61
-321	1.162	0.21	1.582	29.51	5.33	40.18
-322	1.225	0.21	1.645	31.12	5.33	41.78
-323	1.287	0.21	1.707	32.69	5.33	43.36
-324	1.35	0.21	1.77	34.29	5.33	44.96
-325	1.475	0.21	1.895	37.47	5.33	48.13
-326	1.6	0.21	2.02	40.64	5.33	51.31
-327	1.725	0.21	2.145	43.82	5.33	54.48
-328	1.85	0.21	2.27	46.99	5.33	57.66
-329	1.975	0.21	2.395	50.17	5.33	60.83
-330	2.1	0.21	2.52	53.34	5.33	64.01
-331	2.225	0.21	2.645	56.52	5.33	67.18
-332	2.35	0.21	2.77	59.69	5.33	70.36
-333	2.475	0.21	2.895	62.87	5.33	73.53
-334	2.6	0.21	3.02	66.04	5.33	76.71
-335	2.725	0.21	3.145	69.22	5.33	79.88
-336	2.85	0.21	3.27	72.39	5.33	83.06
-337	2.975	0.21	3.395	75.57	5.33	86.23
-338	3.1	0.21	3.52	78.74	5.33	89.41
-339	3.225	0.21	3.645	81.91	5.33	92.58
-340	3.35	0.21	3.77	85.09	5.33	95.76
-341	3.475	0.21	3.895	88.27	5.33	98.93
-342	3.6	0.21	4.02	91.44	5.33	102.1
-343	3.725	0.21	4.145	94.62	5.33	105.3
-344	3.85	0.21	4.27	97.79	5.33	108.5
-345	3.975	0.21	4.395	101	5.33	111.6
-346	4.1	0.21	4.52	104.1	5.33	114.8
-347	4.225	0.21	4.645	107.3	5.33	118
-348	4.35	0.21	4.77	110.5	5.33	121.2
-349	4.475	0.21	4.895	113.7	5.33	124.3
-350	4.6	0.21	5.02	116.8	5.33	127.5
-351	4.725	0.21	5.145	120	5.33	130.7
-352	4.85	0.21	5.27	123.2	5.33	133.9
-353	4.975	0.21	5.395	126.4	5.33	137
-354	5.1	0.21	5.52	129.5	5.33	140.2
-355	5.225	0.21	5.645	132.7	5.33	143.4
-356	5.35	0.21	5.77	135.9	5.33	146.6
-357	5.475	0.21	5.895	139.1	5.33	149.7
-358	5.6	0.21	6.02	142.2	5.33	152.9
-359	5.725	0.21	6.145	145.4	5.33	156.1
-360	5.85	0.21	6.27	148.6	5.33	159.3
-361	5.975	0.21	6.395	151.8	5.33	162.4
-362	6.225	0.21	6.645	158.1	5.33	168.8
-363	6.475	0.21	6.895	164.5	5.33	175.1
-364	6.725	0.21	7.145	170.8	5.33	181.5
-365	6.975	0.21	7.395	177.2	5.33	187.8
-366	7.225	0.21	7.645	183.5	5.33	194.2
-367	7.475	0.21	7.895	189.9	5.33	200.5
-368	7.725	0.21	8.145	196.2	5.33	206.9
-369	7.975	0.21	8.395	202.6	5.33	213.2
-370	8.225	0.21	8.645	208.9	5.33	219.6
-371	8.475	0.21	8.895	215.3	5.33	225.9
-372	8.725	0.21	9.145	221.6	5.33	232.3
-373	8.975	0.21	9.395	228	5.33	238.6
-374	9.225	0.21	9.645	234.3	5.33	245
-375	9.475	0.21	9.895	240.7	5.33	251.3
-376	9.725	0.21	10.15	247	5.33	257.7
-377	9.975	0.21	10.4	253.4	5.33	264
-378	10.48	0.21	10.9	266.1	5.33	276.7
-379	10.98	0.21	11.4	278.8	5.33	289.4
-380	11.48	0.21	11.9	291.5	5.33	302.1
-381	11.98	0.21	12.4	304.2	5.33	314.8
-382	12.98	0.21	13.4	329.6	5.33	340.2
-383	13.98	0.21	14.4	355	5.33	365.6
-384	14.98	0.21	15.4	380.4	5.33	391
-385	15.96	0.21	16.38	405.3	5.33	415.9
-386	16.96	0.21	17.38	430.7	5.33	441.3
-387	17.96	0.21	18.38	456.1	5.33	466.7
-388	18.96	0.21	19.38	481.5	5.33	492.1
-389	19.96	0.21	20.38	506.9	5.33	517.5
-390	20.96	0.21	21.38	532.3	5.33	542.9
-391	21.96	0.21	22.38	557.7	5.33	568.3
-392	22.94	0.21	23.36	582.7	5.33	593.3
-393	23.94	0.21	24.36	608.1	5.33	618.7
-394	24.94	0.21	25.36	633.5	5.33	644.1
-395	25.94	0.21	26.36	658.9	5.33	669.5

AS568 400 series (0.275 in cross-section)

Dash	ID (in)	CS (in)	OD (in)	ID (mm)	CS (mm)	OD (mm)
-425	4.475	0.275	5.025	113.7	6.99	127.6
-426	4.6	0.275	5.15	116.8	6.99	130.8
-427	4.725	0.275	5.275	120	6.99	134
-428	4.85	0.275	5.4	123.2	6.99	137.2
-429	4.975	0.275	5.525	126.4	6.99	140.3
-430	5.1	0.275	5.65	129.5	6.99	143.5
-431	5.225	0.275	5.775	132.7	6.99	146.7
-432	5.35	0.275	5.9	135.9	6.99	149.9
-433	5.475	0.275	6.025	139.1	6.99	153
-434	5.6	0.275	6.15	142.2	6.99	156.2
-435	5.725	0.275	6.275	145.4	6.99	159.4
-436	5.85	0.275	6.4	148.6	6.99	162.6
-437	5.975	0.275	6.525	151.8	6.99	165.7
-438	6.225	0.275	6.775	158.1	6.99	172.1
-439	6.475	0.275	7.025	164.5	6.99	178.4
-440	6.725	0.275	7.275	170.8	6.99	184.8
-441	6.975	0.275	7.525	177.2	6.99	191.1
-442	7.225	0.275	7.775	183.5	6.99	197.5
-443	7.475	0.275	8.025	189.9	6.99	203.8
-444	7.725	0.275	8.275	196.2	6.99	210.2
-445	7.975	0.275	8.525	202.6	6.99	216.5
-446	8.475	0.275	9.025	215.3	6.99	229.2
-447	8.975	0.275	9.525	228	6.99	241.9
-448	9.475	0.275	10.03	240.7	6.99	254.6
-449	9.975	0.275	10.53	253.4	6.99	267.3
-450	10.48	0.275	11.03	266.1	6.99	280
-451	10.98	0.275	11.53	278.8	6.99	292.7
-452	11.48	0.275	12.03	291.5	6.99	305.4
-453	11.98	0.275	12.53	304.2	6.99	318.1
-454	12.48	0.275	13.03	316.9	6.99	330.8
-455	12.98	0.275	13.53	329.6	6.99	343.5
-456	13.48	0.275	14.03	342.3	6.99	356.2
-457	13.98	0.275	14.53	355	6.99	368.9
-458	14.48	0.275	15.03	367.7	6.99	381.6
-459	14.98	0.275	15.53	380.4	6.99	394.3
-460	15.48	0.275	16.03	393.1	6.99	407
-461	15.96	0.275	16.51	405.3	6.99	419.2
-462	16.46	0.275	17.01	418	6.99	431.9
-463	16.96	0.275	17.51	430.7	6.99	444.6
-464	17.46	0.275	18.01	443.4	6.99	457.3
-465	17.96	0.275	18.51	456.1	6.99	470
-466	18.46	0.275	19.01	468.8	6.99	482.7
-467	18.96	0.275	19.51	481.5	6.99	495.4
-468	19.46	0.275	20.01	494.2	6.99	508.1
-469	19.96	0.275	20.51	506.9	6.99	520.8
-470	20.96	0.275	21.51	532.3	6.99	546.2
-471	21.96	0.275	22.51	557.7	6.99	571.6
-472	22.94	0.275	23.49	582.7	6.99	596.6
-473	23.94	0.275	24.49	608.1	6.99	622
-474	24.94	0.275	25.49	633.5	6.99	647.4
-475	25.94	0.275	26.49	658.9	6.99	672.8

Nominal dimensions of the standard AS568 sizes, in inches with the millimetre equivalents. Tolerances vary with size; see the O-ring maker’s data for the limits.

Frequently asked questions

What size is a -210 O-ring?

An AS568 -210 O-ring has an inside diameter of 0.734 inch (18.64 mm) and a cross-section of 0.139 inch (3.53 mm), so its outside diameter is 1.012 inch (25.7 mm).

How do I measure an O-ring to find its size?

Measure the inside diameter across the opening, and the cross-section across the thickness of the cord, ideally with calipers and on a ring that is not stretched. Enter both in the finder above and it returns the closest standard dash numbers. A used ring that has swollen or stretched will measure a little larger than a new one.

What do the numbers in the dash number mean?

The three digits are a size code. The first digit gives the cross-section series, so -2xx sizes all have the same cord thickness, and the rest of the number is the rank of the size within the series, from small to large inside diameter. The number does not equal the diameter in any unit.

Is AS568 the same as a metric O-ring?

No. AS568 is an inch series. Metric O-rings (ISO 3601) use whole-millimetre cross-sections such as 2 mm, 3 mm or 5 mm and their own inside diameters. A few sizes are close enough to interchange in a given groove, but check the dimensions rather than assuming.

Does the dash number tell me the material?

No. The dash number is only the size. The material (nitrile, Viton, EPDM, silicone and so on) and the hardness are specified separately, and a seal should be chosen for the fluid, the temperature and the pressure.

O-Ring Size Chart and Finder (AS568)