ISO 3601 Metric O-Ring Standard

The international metric reference for O-ring dimensions, tolerances and gland design.

Size ID	Inside Diameter (mm)	Cross Section (mm)	Tolerance Class	Action
1.80x1.80	1.80	1.80	N	View
2.00x1.80	2.00	1.80	N	View
2.24x1.80	2.24	1.80	N	View
2.50x1.80	2.50	1.80	N	View
2.80x1.80	2.80	1.80	N	View
3.15x1.80	3.15	1.80	N	View
3.55x1.80	3.55	1.80	N	View
3.75x1.80	3.75	1.80	N	View
4.00x1.80	4.00	1.80	N	View
4.50x1.80	4.50	1.80	N	View
4.75x1.80	4.75	1.80	N	View
4.87x1.80	4.87	1.80	N	View
5.00x1.80	5.00	1.80	N	View
5.15x1.80	5.15	1.80	N	View
5.30x1.80	5.30	1.80	N	View
5.60x1.80	5.60	1.80	N	View
6.00x1.80	6.00	1.80	N	View
6.30x1.80	6.30	1.80	N	View
6.70x1.80	6.70	1.80	N	View
6.90x1.80	6.90	1.80	N	View
7.10x1.80	7.10	1.80	N	View
7.50x1.80	7.50	1.80	N	View
8.00x1.80	8.00	1.80	N	View
8.50x1.80	8.50	1.80	N	View
8.75x1.80	8.75	1.80	N	View
9.00x1.80	9.00	1.80	N	View
9.50x1.80	9.50	1.80	N	View
10.00x1.80	10.00	1.80	N	View
10.60x1.80	10.60	1.80	N	View
11.20x1.80	11.20	1.80	N	View
11.60x1.80	11.60	1.80	N	View
11.80x1.80	11.80	1.80	N	View
12.10x1.80	12.10	1.80	N	View
12.50x1.80	12.50	1.80	N	View
13.20x1.80	13.20	1.80	N	View
14.00x1.80	14.00	1.80	N	View
14.50x1.80	14.50	1.80	N	View
15.00x1.80	15.00	1.80	N	View
15.50x1.80	15.50	1.80	N	View
16.00x1.80	16.00	1.80	N	View
17.00x1.80	17.00	1.80	N	View
18.00x1.80	18.00	1.80	N	View
19.00x1.80	19.00	1.80	N	View
20.00x1.80	20.00	1.80	N	View
21.20x1.80	21.20	1.80	N	View
22.40x1.80	22.40	1.80	N	View
23.00x1.80	23.00	1.80	N	View
23.60x1.80	23.60	1.80	N	View
24.30x1.80	24.30	1.80	N	View
25.00x1.80	25.00	1.80	N	View
25.80x1.80	25.80	1.80	N	View
26.50x1.80	26.50	1.80	N	View
27.30x1.80	27.30	1.80	N	View
28.00x1.80	28.00	1.80	N	View
30.00x1.80	30.00	1.80	N	View
31.50x1.80	31.50	1.80	N	View
32.50x1.80	32.50	1.80	N	View
33.50x1.80	33.50	1.80	N	View
34.50x1.80	34.50	1.80	N	View
35.50x1.80	35.50	1.80	N	View
36.50x1.80	36.50	1.80	N	View
37.50x1.80	37.50	1.80	N	View
38.70x1.80	38.70	1.80	N	View
40.00x1.80	40.00	1.80	N	View
41.20x1.80	41.20	1.80	N	View
42.50x1.80	42.50	1.80	N	View
43.70x1.80	43.70	1.80	N	View
45.00x1.80	45.00	1.80	N	View
46.20x1.80	46.20	1.80	N	View
47.50x1.80	47.50	1.80	N	View
48.70x1.80	48.70	1.80	N	View
50.00x1.80	50.00	1.80	N	View
51.50x1.80	51.50	1.80	N	View
53.00x1.80	53.00	1.80	N	View
54.50x1.80	54.50	1.80	N	View
56.00x1.80	56.00	1.80	N	View
58.00x1.80	58.00	1.80	N	View
60.00x1.80	60.00	1.80	N	View
61.50x1.80	61.50	1.80	N	View
63.00x1.80	63.00	1.80	N	View
65.00x1.80	65.00	1.80	N	View
67.00x1.80	67.00	1.80	N	View
69.00x1.80	69.00	1.80	N	View
71.00x1.80	71.00	1.80	N	View
73.00x1.80	73.00	1.80	N	View
75.00x1.80	75.00	1.80	N	View
77.50x1.80	77.50	1.80	N	View
80.00x1.80	80.00	1.80	N	View
82.50x1.80	82.50	1.80	N	View
85.00x1.80	85.00	1.80	N	View
87.50x1.80	87.50	1.80	N	View
90.00x1.80	90.00	1.80	N	View
92.50x1.80	92.50	1.80	N	View
95.00x1.80	95.00	1.80	N	View
97.50x1.80	97.50	1.80	N	View
100.00x1.80	100.00	1.80	N	View
103.00x1.80	103.00	1.80	N	View
106.00x1.80	106.00	1.80	N	View
109.00x1.80	109.00	1.80	N	View
112.00x1.80	112.00	1.80	N	View
115.00x1.80	115.00	1.80	N	View
118.00x1.80	118.00	1.80	N	View
122.00x1.80	122.00	1.80	N	View
125.00x1.80	125.00	1.80	N	View
128.00x1.80	128.00	1.80	N	View
132.00x1.80	132.00	1.80	N	View
136.00x1.80	136.00	1.80	N	View
140.00x1.80	140.00	1.80	N	View
145.00x1.80	145.00	1.80	N	View
150.00x1.80	150.00	1.80	N	View
155.00x1.80	155.00	1.80	N	View
160.00x1.80	160.00	1.80	N	View
165.00x1.80	165.00	1.80	N	View
170.00x1.80	170.00	1.80	N	View
175.00x1.80	175.00	1.80	N	View
180.00x1.80	180.00	1.80	N	View
185.00x1.80	185.00	1.80	N	View
190.00x1.80	190.00	1.80	N	View
195.00x1.80	195.00	1.80	N	View
200.00x1.80	200.00	1.80	N	View
206.00x1.80	206.00	1.80	N	View
212.00x1.80	212.00	1.80	N	View
218.00x1.80	218.00	1.80	N	View
224.00x1.80	224.00	1.80	N	View
230.00x1.80	230.00	1.80	N	View
236.00x1.80	236.00	1.80	N	View
243.00x1.80	243.00	1.80	N	View
250.00x1.80	250.00	1.80	N	View
7.50x2.65	7.50	2.65	N	View
8.00x2.65	8.00	2.65	N	View
8.50x2.65	8.50	2.65	N	View
9.00x2.65	9.00	2.65	N	View
9.50x2.65	9.50	2.65	N	View
10.00x2.65	10.00	2.65	N	View
10.60x2.65	10.60	2.65	N	View
11.20x2.65	11.20	2.65	N	View
11.80x2.65	11.80	2.65	N	View
12.50x2.65	12.50	2.65	N	View
13.20x2.65	13.20	2.65	N	View
14.00x2.65	14.00	2.65	N	View
15.00x2.65	15.00	2.65	N	View
16.00x2.65	16.00	2.65	N	View
17.00x2.65	17.00	2.65	N	View
18.00x2.65	18.00	2.65	N	View
19.00x2.65	19.00	2.65	N	View
20.00x2.65	20.00	2.65	N	View
21.20x2.65	21.20	2.65	N	View
22.40x2.65	22.40	2.65	N	View
23.60x2.65	23.60	2.65	N	View
25.00x2.65	25.00	2.65	N	View
25.80x2.65	25.80	2.65	N	View
26.50x2.65	26.50	2.65	N	View
28.00x2.65	28.00	2.65	N	View
30.00x2.65	30.00	2.65	N	View
31.50x2.65	31.50	2.65	N	View
32.50x2.65	32.50	2.65	N	View
33.50x2.65	33.50	2.65	N	View
34.50x2.65	34.50	2.65	N	View
35.50x2.65	35.50	2.65	N	View
36.50x2.65	36.50	2.65	N	View
37.50x2.65	37.50	2.65	N	View
38.70x2.65	38.70	2.65	N	View
40.00x2.65	40.00	2.65	N	View
41.20x2.65	41.20	2.65	N	View
42.50x2.65	42.50	2.65	N	View
43.70x2.65	43.70	2.65	N	View
45.00x2.65	45.00	2.65	N	View
46.20x2.65	46.20	2.65	N	View
47.50x2.65	47.50	2.65	N	View
48.70x2.65	48.70	2.65	N	View
50.00x2.65	50.00	2.65	N	View
51.50x2.65	51.50	2.65	N	View
53.00x2.65	53.00	2.65	N	View
54.50x2.65	54.50	2.65	N	View
56.00x2.65	56.00	2.65	N	View
58.00x2.65	58.00	2.65	N	View
60.00x2.65	60.00	2.65	N	View
61.50x2.65	61.50	2.65	N	View
63.00x2.65	63.00	2.65	N	View
65.00x2.65	65.00	2.65	N	View
67.00x2.65	67.00	2.65	N	View
69.00x2.65	69.00	2.65	N	View
71.00x2.65	71.00	2.65	N	View
73.00x2.65	73.00	2.65	N	View
75.00x2.65	75.00	2.65	N	View
77.50x2.65	77.50	2.65	N	View
80.00x2.65	80.00	2.65	N	View
82.50x2.65	82.50	2.65	N	View
85.00x2.65	85.00	2.65	N	View
87.50x2.65	87.50	2.65	N	View
90.00x2.65	90.00	2.65	N	View
92.50x2.65	92.50	2.65	N	View
95.00x2.65	95.00	2.65	N	View
97.50x2.65	97.50	2.65	N	View
100.00x2.65	100.00	2.65	N	View
103.00x2.65	103.00	2.65	N	View
106.00x2.65	106.00	2.65	N	View
109.00x2.65	109.00	2.65	N	View
112.00x2.65	112.00	2.65	N	View
115.00x2.65	115.00	2.65	N	View
118.00x2.65	118.00	2.65	N	View
122.00x2.65	122.00	2.65	N	View
125.00x2.65	125.00	2.65	N	View
128.00x2.65	128.00	2.65	N	View
132.00x2.65	132.00	2.65	N	View
136.00x2.65	136.00	2.65	N	View
140.00x2.65	140.00	2.65	N	View
145.00x2.65	145.00	2.65	N	View
150.00x2.65	150.00	2.65	N	View
155.00x2.65	155.00	2.65	N	View
160.00x2.65	160.00	2.65	N	View
165.00x2.65	165.00	2.65	N	View
170.00x2.65	170.00	2.65	N	View
175.00x2.65	175.00	2.65	N	View
180.00x2.65	180.00	2.65	N	View
185.00x2.65	185.00	2.65	N	View
190.00x2.65	190.00	2.65	N	View
195.00x2.65	195.00	2.65	N	View
200.00x2.65	200.00	2.65	N	View
206.00x2.65	206.00	2.65	N	View
212.00x2.65	212.00	2.65	N	View
218.00x2.65	218.00	2.65	N	View
224.00x2.65	224.00	2.65	N	View
230.00x2.65	230.00	2.65	N	View
236.00x2.65	236.00	2.65	N	View
243.00x2.65	243.00	2.65	N	View
250.00x2.65	250.00	2.65	N	View
26.00x3.55	26.00	3.55	N	View
28.00x3.55	28.00	3.55	N	View
30.00x3.55	30.00	3.55	N	View
31.50x3.55	31.50	3.55	N	View
32.50x3.55	32.50	3.55	N	View
33.50x3.55	33.50	3.55	N	View
34.50x3.55	34.50	3.55	N	View
35.50x3.55	35.50	3.55	N	View
36.50x3.55	36.50	3.55	N	View
37.50x3.55	37.50	3.55	N	View
38.70x3.55	38.70	3.55	N	View
40.00x3.55	40.00	3.55	N	View
41.20x3.55	41.20	3.55	N	View
42.50x3.55	42.50	3.55	N	View
43.70x3.55	43.70	3.55	N	View
45.00x3.55	45.00	3.55	N	View
46.20x3.55	46.20	3.55	N	View
47.50x3.55	47.50	3.55	N	View
48.70x3.55	48.70	3.55	N	View
50.00x3.55	50.00	3.55	N	View
51.50x3.55	51.50	3.55	N	View
53.00x3.55	53.00	3.55	N	View
54.50x3.55	54.50	3.55	N	View
56.00x3.55	56.00	3.55	N	View
58.00x3.55	58.00	3.55	N	View
60.00x3.55	60.00	3.55	N	View
61.50x3.55	61.50	3.55	N	View
63.00x3.55	63.00	3.55	N	View
65.00x3.55	65.00	3.55	N	View
67.00x3.55	67.00	3.55	N	View
69.00x3.55	69.00	3.55	N	View
71.00x3.55	71.00	3.55	N	View
73.00x3.55	73.00	3.55	N	View
75.00x3.55	75.00	3.55	N	View
77.50x3.55	77.50	3.55	N	View
80.00x3.55	80.00	3.55	N	View
82.50x3.55	82.50	3.55	N	View
85.00x3.55	85.00	3.55	N	View
87.50x3.55	87.50	3.55	N	View
90.00x3.55	90.00	3.55	N	View
92.50x3.55	92.50	3.55	N	View
95.00x3.55	95.00	3.55	N	View
97.50x3.55	97.50	3.55	N	View
100.00x3.55	100.00	3.55	N	View
103.00x3.55	103.00	3.55	N	View
106.00x3.55	106.00	3.55	N	View
109.00x3.55	109.00	3.55	N	View
112.00x3.55	112.00	3.55	N	View
115.00x3.55	115.00	3.55	N	View
118.00x3.55	118.00	3.55	N	View
122.00x3.55	122.00	3.55	N	View
125.00x3.55	125.00	3.55	N	View
128.00x3.55	128.00	3.55	N	View
132.00x3.55	132.00	3.55	N	View
136.00x3.55	136.00	3.55	N	View
140.00x3.55	140.00	3.55	N	View
145.00x3.55	145.00	3.55	N	View
150.00x3.55	150.00	3.55	N	View
155.00x3.55	155.00	3.55	N	View
160.00x3.55	160.00	3.55	N	View
165.00x3.55	165.00	3.55	N	View
170.00x3.55	170.00	3.55	N	View
175.00x3.55	175.00	3.55	N	View
180.00x3.55	180.00	3.55	N	View
185.00x3.55	185.00	3.55	N	View
190.00x3.55	190.00	3.55	N	View
195.00x3.55	195.00	3.55	N	View
200.00x3.55	200.00	3.55	N	View

ISO 3601 FAQ

What is the difference between ISO 3601-1 and ISO 3601-2?

ISO 3601-1 defines the O-ring dimensions and tolerances. ISO 3601-2 defines the groove dimensions, surface finishes, and design rules for installing those O-rings in housings.

Are DIN 3771 and ISO 3601 sizes the same?

Yes. DIN 3771 metric O-ring sizes are dimensionally aligned with ISO 3601-1. For general engineering, parts labeled to either standard are interchangeable.

What are metric O-ring groove dimensions?

For a static seal, the groove width is typically 1.15 to 1.25 times the O-ring cross-section, with a groove depth that produces 15-20% squeeze. Dynamic grooves are wider to reduce friction.

Can I use an ISO 3601 O-ring in an AS568 gland?

For common sizes, the dimensions are close enough to be interchangeable, but not identical. In critical applications, always design the gland to match the exact standard you are specifying.

What is the largest metric O-ring size in ISO 3601?

ISO 3601-1 covers sizes up to approximately 670 mm inside diameter. Larger sizes are manufactured as custom-molded or spliced/vulcanized rings outside the standard tables.