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O-Ring Gland Squeeze and Gland Fill Calculator

Squeeze and gland fill are the first two numbers anyone checks on an O-ring groove. This calculator takes the O-ring cross-section, groove depth and width with their tolerances and returns nominal and worst-case squeeze and fill, including volume swell in the service fluid.

Your numbers

O-ring cross-section (nominal)

AS568 2xx series is 0.139 in nominal.

Cross-section tolerance (+/-)

Plus or minus tolerance from the AS568 or supplier drawing.

Groove depth (nominal)

Measured in the direction of compression, including any surface finish allowance.

Groove depth tolerance (+/-)

Groove width

Width of the groove at the base, before backup ring allowance.

Volume swell in service fluid

5 %

Elastomer volume change from the compatibility data for your fluid.

Your results

Nominal squeeze

24.5%

Squeeze = (cross-section minus groove depth) divided by cross-section.

Worst-case gland fill

87.6%

Largest O-ring, swollen, in the smallest gland. Keep at or below about 85 percent.

Minimum squeeze (worst case)

20.7%

Smallest O-ring in the deepest groove. Must stay above the leak threshold.

Maximum squeeze (worst case)

28%

Largest O-ring in the shallowest groove. Drives assembly force and compression set.

O-ring cross-section area (nominal)

0.0152

Circle area in square inches.

Gland cross-section area (nominal)

0.0196

Depth times width, square inches. Corner radii are ignored.

Nominal gland fill

81.1%

Seal area including swell over gland area.

Planar approximation of an O-ring in a rectangular gland. Dynamic seals, backup rings, pressure energisation and radial stretch are not modelled. Confirm against the seal supplier design guide.

Save results:

Squeeze and worst-case fill vs groove depth

Sweeps Groove depth (nominal) from 0.095 to 0.125, holding your other inputs fixed.

Want seal data pulled straight from your ERP?

An optional walkthrough of connecting item masters and drawings to a private, read-only assistant for engineering checks.

Optional. The tool and every export work without this. No spam.

How to use it

Enter the nominal O-ring cross-section and the groove depth from your drawing, then both tolerances. Add the groove width and the percent volume swell you expect from the fluid compatibility table. The primary results are nominal squeeze and worst-case gland fill. Check the minimum and maximum squeeze lines against your design window, then use the sweep chart to see how much margin you have if the groove depth drifts in machining.

Use the groove depth the inspector will actually measure, not the CAD envelope.
Set swell to zero for dry or air service, and to the compatibility value for oils and fuels.
Use the chart to find the depth range where both squeeze and fill stay inside limits.

The formulas

Squeeze is (CS - depth) / CS, expressed in percent. Minimum squeeze pairs the smallest O-ring (CS minus tolerance) with the deepest groove (depth plus tolerance); maximum squeeze pairs the largest O-ring with the shallowest groove. Gland fill is the O-ring circle area, pi/4 times CS squared, multiplied by one plus swell, divided by the rectangular gland area, depth times width. Worst-case fill uses the largest O-ring and the shallowest groove. Corner radii add a little gland area, so this is conservative.

Typical design windows

Common guidance for static seals is roughly 15 to 30 percent squeeze, and for reciprocating dynamic seals roughly 10 to 20 percent, with gland fill held at or below about 85 percent so there is room for thermal expansion and swell. Treat these as starting points and defer to your seal supplier or the governing design standard. Low squeeze leaks, especially after compression set; high squeeze raises friction, installation force and permanent set.

Minimum squeeze below about 10 percent in a static groove is a leak risk.
Fill above 100 percent means the seal has no room and will extrude or damage on assembly.
Check fill at the highest service temperature as well as room temperature.

Common mistakes

The most frequent error is judging a design on nominal squeeze only. With a 0.139 in cross-section and a 0.105 in groove, nominal squeeze is about 24 percent, but the tolerance stack can move it several points either way. The second is forgetting swell, which is the reason a groove that looks fine in air jams in oil. The third is using a groove width that includes the backup ring space, which understates fill.

Frequently Asked Questions

What is a good O-ring squeeze percentage?

For static seals about 15 to 30 percent is common, and for reciprocating dynamic seals about 10 to 20 percent. Harder compounds and larger cross-sections often sit at the lower end. Your supplier design guide for the specific compound and application takes priority over these general ranges.

How is gland fill calculated?

Divide the O-ring cross-section area, pi over 4 times CS squared, by the gland area, depth times width, and multiply by 100. Add volume swell to the seal area. The usual target is at or below about 85 percent so the seal has room to expand.

Why does worst-case fill matter more than nominal?

Seals fail at the extremes of the tolerance stack, not at nominal. The largest O-ring in the shallowest groove with maximum swell is the case that causes pinching, extrusion and high assembly force, so that is the case to design against.

Does this work for face seals and radial seals?

The squeeze and fill formulas apply to both because they depend on cross-section and groove geometry. Radial seals also have stretch and diametral clearance effects, which the stretch and thermal clearance calculators on this site cover separately.

If seal quotes and engineering checks live in separate spreadsheets, we can connect your ERP item data to a read-only assistant that pulls the right dash size and groove data when a quote is built.

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