O-Ring Gland Calculator

First-pass O-ring squeeze, stretch and gland fill from free ID, cross section, installed diameter, gland depth and gland width. Metric and imperial. Free, no signup.

Inputs

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O-ring free ID (ID)

Inside diameter of the free O-ring before installation.

Cross section (CS)

O-ring cord diameter.

Installed diameter (D_i)

Diameter the O-ring stretches over in the gland.

Gland depth (h)

Radial gland depth after installation; this sets squeeze.

Gland width (w)

Axial groove width available to the O-ring.

Results

Default result

Edit inputs

Squeeze(S)

20%

Pass

Squeeze = (cross section - gland depth) / cross section.

Typical static radial target is roughly 10-30%.

Also computed

Gland fill(GF)61.36%

Gland fill = O-ring cross-section area / gland rectangular area.

Many static glands target below about 85% fill.

Stretch(ST)2%

Keep stretch modest; large stretch reduces cross section.

O-ring area(A_o)3.142mm²

Gland area(A_g)5.12mm²

Compressed height(h)1.6mm

Method notes 3 notes

This is a geometric gland check for squeeze, stretch and fill. It does not replace the Parker/AS568 or manufacturer gland tables.
High gland fill leaves little room for thermal expansion, swell and tolerance stack-up; fill above about 85% is usually a warning for static glands.
Dynamic seals, pressure direction, extrusion gaps, backup rings, compound swell, temperature, surface finish and friction are not included.

O-ring gland geometry is checked with three first-pass ratios: squeeze = (CS − gland depth)/CS, stretch = (installed diameter − free ID)/free ID, and gland fill = (πCS²/4)/(gland depth × width). This calculator returns all three, plus O-ring area and gland area, so you can screen a radial seal groove before using a manufacturer table.

How to use this calculator

Enter O-ring size. Use the free inside diameter and cord cross section.
Enter installed diameter. Use the diameter the O-ring stretches over in the gland.
Enter gland dimensions. Use radial gland depth and axial gland width.
Check squeeze. Compare squeeze percentage to the range your seal handbook recommends.
Check fill. Keep enough void volume for swell, heat and tolerance stack-up.

How it works

Squeeze is the radial compression of the O-ring cross section: squeeze = (CS - gland depth) / CS x 100 Stretch compares the installed diameter with the free O-ring ID: stretch = (installed diameter - free ID) / free ID x 100.

Gland fill compares the O-ring cross-section area with the rectangular groove area: fill = (pi x CS^2 / 4) / (depth x width) x 100. High fill can leave no room for thermal expansion, fluid swell and tolerances.

Worked example

Verified against the live calculator

A 20 mm ID O-ring with 2 mm cross section installed over 20.4 mm has 2% stretch.

With 1.6 mm gland depth, squeeze is 20%. With 3.2 mm gland width, gland fill is (pi x 2^2 / 4) / (1.6 x 3.2) = 61.36%.

Frequently asked questions

How do you calculate O-ring squeeze?

O-ring squeeze percentage is (cross section - gland depth) / cross section * 100. It measures how much the cord is compressed after installation.

How do you calculate O-ring gland fill?

Gland fill is the O-ring cross-section area divided by the available gland area: (pi*CS^2/4) / (gland depth * gland width) * 100.

What gland fill is too high?

Many static O-ring gland guides warn above roughly 85% fill because thermal expansion, fluid swell and tolerance stack-up need spare volume.

What O-ring stretch is acceptable?

Stretch should usually be modest. This calculator warns above 5% stretch, but final limits depend on seal type, compound, application and manufacturer guidance.

Does this replace an O-ring handbook?

No. This is a geometric squeeze, stretch and fill check. Use Parker, AS568 or manufacturer gland tables for final groove dimensions and extrusion-gap limits.

Does this work in inches?

Yes. Toggle units to enter the free ID, cross section and gland dimensions in inches. Percent results stay the same.

Method & assumptions

Geometric radial-gland check only: squeeze, stretch and fill.
Gland area is treated as a rectangular depth by width area.
Warnings are broad first-pass bands, not a substitute for manufacturer gland tables.
Dynamic friction, extrusion gap, backup rings, compound swell, pressure direction, temperature and surface finish are not modeled.

O-Ring Gland Calculator

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