What size is an AS568-212 o-ring?

An AS568-212 o-ring has an inside diameter of 0.8590 in (21.820 mm) and a cross-section of 0.1390 in (3.530 mm), giving an outside diameter of 1.1370 in (28.880 mm).

What is an AS568-212 o-ring in mm?

21.820 mm inside diameter × 3.530 mm cross-section, 28.880 mm outside diameter. AS568 is an inch standard, so these are exact conversions rather than metric nominal sizes.

What is the tolerance on an AS568-212 o-ring?

AS568 allows ± 0.0098 in (± 0.250 mm) on the inside diameter and ± 0.0039 in (± 0.100 mm) on the cross-section, measured free-state.

What groove depth does an AS568-212 o-ring need?

For face seal, static service, a gland depth of 0.0973 to 0.1112 in (2.471 to 2.824 mm), which gives 20–30% squeeze on the 0.1390 in cross-section. Groove width and corner radius come from the seal manufacturer's chart.

Which AS568 series is the AS568-212 o-ring in?

Dash 212 is in the 201-284 band — AS568 1/8 in series, a 0.139 in cross-section. Every size in that band shares the same cross-section and therefore the same gland depth.

AS568 · dash 212 · 0.139 in cross-section

AS568-212 O-Ring Size — ID, Cross-Section, OD and Gland Data

https://shopmath.org/o-rings/as568-212 · data verified August 1, 2026

An AS568-212 o-ring is 0.8590 in (21.820 mm) inside diameter with a 0.1390 in (3.530 mm) cross-section, giving a 1.1370 in (28.880 mm) outside diameter. Static glands for this cross-section run 0.0973–0.1112 in deep. Dimensions are free-state, before installation.

Dash: 212
ID: 0.8590 in
CS: 0.1390 in
OD: 1.1370 in
Series: 201-284

AS568-212 o-ring · inside Ø × cross-section

0.8590 × 0.1390 in

Inside Ø: 21.820mm
Cross-section: 3.530mm
Outside Ø: 28.880mm

Free-state dimensions with AS568 tolerances of ± 0.0098 in on the ID and ± 0.0039 in on the cross-section.

AS568-212 O-Ring Dimensions and Tolerances

An AS568 o-ring is specified by its inside diameter and cross-section; the outside diameter follows from them. Tolerances are the AS568 free-state limits, measured uninstalled.

AS568-212 o-ring — inside diameter, cross-section and outside diameter with tolerances
Dimension	Inch	Millimetre
Inside diameter (ID)	0.8590 ± 0.0098	21.820 ± 0.250
Cross-section (CS / W)	0.1390 ± 0.0039	3.530 ± 0.100
Outside diameter (OD)	1.1370	28.880

OD = ID + 2 × CS. Elastomer parts are measured free-state and relax over time; the tolerances above are manufacturing limits, not the installed dimensions.

AS568-212 O-Ring Size in Millimetres

AS568 is an inch standard. These are the same dimensions converted exactly (1 in = 25.4 mm) — an AS568 size is not interchangeable with an ISO 3601 metric size that happens to be close.

AS568-212 o-ring — metric dimensions
Dimension	Inch	Millimetre
Nominal ID × CS	0.8590 × 0.1390 in	21.820 × 3.530 mm
Nominal OD × CS	1.1370 × 0.1390 in	28.880 × 3.530 mm

Metric figures are conversions of the AS568 inch dimensions, rounded to 0.01 mm as the source data carries them. A metric o-ring called out as 25 × 3.5 mm is a different part.

Static Gland Depth for a AS568-212 O-Ring

Squeeze and gland depth for the 0.139 in cross-section band this size belongs to, from MIL-G-5514G. Depth is what the groove is cut to; squeeze is what the ring gives up to seal.

Static gland squeeze and depth for the 201-284 cross-section series
Property	Squeeze		Gland depth
Application	%	in	in	mm
Face seal, static	20–30	0.0278–0.0417	0.0973–0.1112	2.471–2.824

Static applications only — this reference carries no verified squeeze band for dynamic (reciprocating or rotary) service, so none is shown. Groove width, corner radius, diametral clearance and back-up ring dimensions are outside the verified dataset and must come from the seal manufacturer's design chart.

AS568 O-Ring Sizes Closest to AS568-212

Ordered by how close the inside diameter is, across every cross-section series. A near-ID match in a different cross-section will not seal the same gland.

AS568 o-ring sizes with an inside diameter closest to AS568-212
Property	Inside Ø		Property	Property	Property
Size	in	mm	Cross-section, in	Outside Ø, in	ID difference, mm
AS568-118	0.8620	21.890	0.1030	1.0680	+0.070
AS568-020	0.8640	21.950	0.0700	1.0040	+0.130
AS568-316	0.8500	21.590	0.2100	1.2700	-0.230
AS568-317	0.9120	23.160	0.2100	1.3320	+1.340
AS568-019	0.8010	20.350	0.0700	0.9410	-1.470
AS568-117	0.7990	20.290	0.1030	1.0050	-1.530

Check the cross-section before substituting: the gland depth is set by cross-section, not by inside diameter.

Sources and Method for the AS568-212 O-Ring Size

Size and tolerancescomputed+compiled

bd_warehouse o-ring_parameters.csv (Apache-2.0) and bckasper3/KasperCalc oring-sizes.js (MIT), agreeing on all 349 sizes; OD computed as ID + 2 x CS

Verified against two independent open datasets agreeing on all 349 sizes; fabricated-dataset negative control passed; 21 checks total

Part computed from the standard's formulas, part compiled from agreeing public sources.

Gland designcomputed

MIL-G-5514G (public domain) gland design criteria; squeeze-percentage bands cross-read from Parker O-Ring Handbook ORD-5700 Design Charts 4-2/4-3 (verification only); depth = CS - CS x squeeze%

Verified against computed depth band brackets the published design-chart band for every series

Computed from the standard's formulas, then checked against published tables.

Formula

Outside diameter

OD  =  ID + 2 × CS

  0.8590 + 2 × 0.1390  =  1.1370 in

Gland depth from squeeze

depth  =  CS − (CS × squeeze%)

Squeeze percentage bands are the MIL-G-5514G static criteria; the depth column is that percentage applied to the nominal cross-section.

Assumptions

Dimensions are free-state, at room temperature, before installation.
Tolerances are AS568 manufacturing limits. Compression set, swell in service fluid and thermal expansion all move the installed dimensions and are properties of the compound, not of the size.
Gland figures are for static service only. MIL-G-5514G is inactive for new design and is used here as a public-domain source for the static squeeze bands.
Dataset scope: A fabricated-dataset negative control is asserted against on every run. EXCLUDED: groove width, corner radius, diametral clearance, back-up ring widths, surface finish, all dynamic glands, the 900-series, and ISO 3601 metric sizes.

Data last verified

August 1, 2026

How this data is built and checked →

How to Cite This AS568-212 O-Ring Reference

Citation

ShopMath. "AS568-212 O-Ring Size — ID, Cross-Section, OD and Gland Data." ShopMath, verified August 1, 2026, https://shopmath.org/o-rings/as568-212

BibTeX

@misc{shopmath-o-rings-as568-212,
  title        = {AS568-212 O-Ring Size — ID, Cross-Section, OD and Gland Data},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/o-rings/as568-212}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/o-rings/as568-212

Common Questions About the AS568-212 O-Ring

What size is an AS568-212 o-ring?: An AS568-212 o-ring has an inside diameter of 0.8590 in (21.820 mm) and a cross-section of 0.1390 in (3.530 mm), giving an outside diameter of 1.1370 in (28.880 mm).
What is an AS568-212 o-ring in mm?: 21.820 mm inside diameter × 3.530 mm cross-section, 28.880 mm outside diameter. AS568 is an inch standard, so these are exact conversions rather than metric nominal sizes.
What is the tolerance on an AS568-212 o-ring?: AS568 allows ± 0.0098 in (± 0.250 mm) on the inside diameter and ± 0.0039 in (± 0.100 mm) on the cross-section, measured free-state.
What groove depth does an AS568-212 o-ring need?: For face seal, static service, a gland depth of 0.0973 to 0.1112 in (2.471 to 2.824 mm), which gives 20–30% squeeze on the 0.1390 in cross-section. Groove width and corner radius come from the seal manufacturer's chart.
Which AS568 series is the AS568-212 o-ring in?: Dash 212 is in the 201-284 band — AS568 1/8 in series, a 0.139 in cross-section. Every size in that band shares the same cross-section and therefore the same gland depth.

Complete AS568 size chart · Every AS568 series