O-Ring Gland / Groove Calculator
Enter your o-ring cross section and inside diameter to instantly calculate recommended gland depth, groove width, corner radius, nominal squeeze, and gland fill percentage. Supports all five AS568 cross-section series in both inches and millimeters, with full coverage of piston, rod, and face seal configurations.
All calculations follow the Parker O-Ring Handbook (ORD 5700) and AS568B gland design guidelines. Results include color-coded status indicators and application-specific warnings for squeeze, fill, and backup ring recommendations.
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How to Use the Gland Calculator
- Enter your o-ring cross section (CS). Use a standard AS568 value — 0.070, 0.103, 0.139, 0.210, or 0.275 inches (1.78, 2.62, 3.53, 5.33, or 6.99 mm). The calculator accepts any value within 0.025″ of a standard series and snaps to the nearest one.
- Enter the o-ring inside diameter (ID). This is the inner circumference diameter of the unstretched o-ring, not the groove or bore diameter. Look it up in our O-Ring Size Search if you have a dash number.
- Select your seal type. Piston seals compress radially into a bore. Rod seals compress radially around a shaft. Face seals compress axially between two flat surfaces. Each type uses a different hardware reference dimension.
- Select static or dynamic. Dynamic (reciprocating) applications require tighter squeeze control to limit friction and heat. Static applications allow more squeeze since there is no sliding motion.
- Select backup rings. Backup rings prevent o-ring extrusion under high pressure. For dynamic applications above 1,500 psi, one backup ring is typically recommended. For pressures above 3,000 psi, use two backup rings — one on each side.
- Click Calculate Gland. The calculator outputs gland depth range, groove width, corner radius, nominal squeeze percentage, and gland fill percentage with color-coded indicators and any applicable warnings.
AS568 Gland Dimensions by Cross Section
The table below summarizes Parker ORD 5700 recommended gland dimensions for all five AS568 cross-section series. Use this as a check against the calculator output or when sizing a gland without a specific o-ring ID in hand.
| CS Series | CS (in / mm) | Gland Depth — Static | Gland Depth — Dynamic | Groove Width (no BU) | Squeeze Range |
|---|---|---|---|---|---|
| -0XX & -1XX e.g. -014, -113 |
0.070″ / 1.78 mm | 0.049 – 0.054″ | 0.050 – 0.055″ | 0.105″ | 21 – 30% Static 21 – 29% Dynamic |
| -1XX e.g. -210, -112 |
0.103″ / 2.62 mm | 0.075 – 0.081″ | 0.080 – 0.086″ | 0.146″ | 21 – 27% Static 17 – 22% Dynamic |
| -2XX e.g. -214, -325 |
0.139″ / 3.53 mm | 0.100 – 0.108″ | 0.110 – 0.116″ | 0.195″ | 22 – 28% Static 17 – 21% Dynamic |
| -3XX e.g. -329, -349 |
0.210″ / 5.33 mm | 0.155 – 0.165″ | 0.170 – 0.176″ | 0.280″ | 21 – 26% Static 16 – 19% Dynamic |
| -4XX e.g. -425, -460 |
0.275″ / 6.99 mm | 0.205 – 0.215″ | 0.225 – 0.235″ | 0.350″ | 22 – 25% Static 15 – 18% Dynamic |
O-Ring Gland Design Fundamentals
Squeeze Percentage
Squeeze is the primary driver of sealing force. It is the amount the o-ring cross section is compressed, expressed as a percentage of the nominal cross section diameter.
For static seals, squeeze typically runs 22–30% depending on cross section. Higher squeeze is acceptable because there is no friction concern. For dynamic seals, squeeze is kept lower — typically 15–22% — to limit friction, heat generation, and seal wear over time.
Too little squeeze allows leakage at low pressures or when the o-ring cold-flows. Too much squeeze overstresses the rubber, accelerates wear on dynamic applications, and can cause extrusion into the clearance gap.
Gland Fill
Gland fill is the percentage of the gland’s cross-sectional area occupied by the o-ring at rest. It is calculated by dividing the o-ring’s circular cross-sectional area by the rectangular area of the gland (gland depth × groove width).
The target range is 65–85%. Below 65%, the seal may roll or lose contact at low pressure. Above 85%, thermal expansion can cause the gland to overfill, pushing the o-ring into the clearance gap and causing extrusion or permanent deformation.
Gland Depth
Gland depth (also called groove depth) is the distance from the sealing surface to the floor of the groove. It directly controls squeeze: a shallower gland produces more squeeze, a deeper gland produces less.
Parker ORD 5700 specifies a minimum and maximum gland depth for each cross section and application type. The calculator outputs the full min/max range along with a recommended midpoint target that keeps squeeze centered in the allowable range.
Groove Width
Groove width must accommodate the compressed o-ring and, if used, backup rings, while maintaining the target gland fill percentage. A groove that is too narrow restricts thermal expansion and increases extrusion risk. A groove that is too wide results in underfill and allows the o-ring to roll or twist.
Width specifications increase significantly when backup rings are added — a single backup ring adds 40–80% to groove width depending on the cross-section series.
Corner Radius
The groove corners must be radiused, not sharp. Sharp corners cause stress concentrations that nick or cut the o-ring during installation. Parker ORD 5700 specifies a minimum corner radius of 0.005″ for small cross sections, increasing to 0.060″ for the 0.275″ CS series. Surface finish of 16–32 RMS is recommended on the groove walls and sealing surfaces for dynamic applications.
Piston, Rod, and Face Seal Configurations
Piston Seals
In a piston seal configuration, the o-ring groove is machined into the outer surface of a piston or plug. The o-ring seals against the inner bore of the surrounding housing. The o-ring ID is typically sized close to the piston OD, and the bore diameter must be large enough to accommodate the o-ring OD plus a small diametral clearance — typically 0.003″ for dynamic and 0.010″ for static. The calculator outputs the minimum bore ID for this configuration.
Rod Seals
In a rod seal (also called a shaft seal or housing seal), the groove is machined into the housing bore, and the o-ring seals against the outside surface of a rod or shaft passing through it. The o-ring ID is sized close to the rod OD. This is the most common configuration for hydraulic cylinders, pneumatic actuators, and rotary shaft seals. The calculator outputs the housing bore ID for this configuration.
Face Seals
Face seals (also called axial seals or flange seals) compress the o-ring between two parallel flat surfaces. Unlike radial seals, there is no clearance gap to worry about on the sides. Groove width is still critical for gland fill but gland depth drives squeeze just as it does in radial seals. Face seals are commonly used on fluid connectors, end caps, valve bonnets, and pipe flanges. No hardware reference dimension is output for this type since the bore or shaft is not involved.
Backup Rings and Extrusion Prevention
Under high pressure, the o-ring attempts to extrude into the diametral clearance gap between the mating hardware surfaces. Once extruded, the o-ring is sheared or nibbled by the reciprocating motion and fails rapidly. Backup rings prevent this by mechanically blocking the clearance gap.
- No Backup Rings Suitable for low-to-medium pressure static applications and dynamic applications below approximately 1,500 psi, provided diametral clearance is held tight (under 0.003″). Material hardness also affects the pressure limit — a 90 Shore A compound resists extrusion at higher pressures than a 70 Shore A.
- 1 Backup Ring The backup ring is placed on the low-pressure side of the o-ring. Extends dynamic service life to approximately 3,000 psi and significantly improves extrusion resistance for static seals. Backup rings are typically made from PTFE or a harder durometer of the same elastomer.
- 2 Backup Rings One backup ring on each side of the o-ring. Required when pressure direction reverses (double-acting cylinders) or for applications above 3,000 psi. Two backup rings substantially increase groove width — factor this into your hardware design early.
O-Ring Material and Durometer Considerations
Gland dimensions are based on the o-ring’s nominal cross section and are largely independent of material. However, material choice does affect several gland design decisions.
Durometer and Squeeze
Harder compounds (80–90 Shore A) resist extrusion better and tolerate higher squeeze without permanent deformation. Softer compounds (50–70 Shore A) conform better to irregular sealing surfaces and require less sealing force, but may need tighter clearance gaps to prevent extrusion at elevated pressures.
Standard o-ring compounds are typically formulated at 70 Shore A for general service. Specialty applications may require 80 or 90 Shore A, particularly for high-pressure dynamic service without backup rings.
Thermal Expansion and Gland Fill
All elastomers expand when heated. Silicone has a particularly high coefficient of thermal expansion and requires the gland fill to be held toward the lower end of the 65–85% target range, especially in high-temperature applications, to leave room for expansion. FKM and EPDM have lower expansion rates and are more forgiving at the upper end of the fill range.
If your application cycles through a wide temperature range, design the gland fill at room temperature and verify that the maximum operating temperature does not cause the fill to exceed 90%.