Definition
Squeeze is the amount by which an O-ring's cross-section (cord diameter, d2) is compressed when the ring is installed in its groove. It is usually expressed as a percentage of the free cord diameter.
Squeeze % = (free cord diameter − gland height) ÷ free cord diameter × 100. The gland height is the radial (or axial, for face seals) space the ring occupies once assembled.
Why it matters
Too little squeeze and the ring cannot maintain contact pressure — the joint leaks, especially as temperature and pressure cycle. Too much squeeze raises internal stress, accelerates compression set, increases friction on dynamic seals and makes extrusion more likely.
Typical ranges
As a guide: radial static seals ~15–25%, dynamic (reciprocating) seals ~8–16%, and face seals in between. Vacuum and specialised applications may sit outside these. Always check the value across the full tolerance stack, not just the nominal.
Calculate it
The radial and face seal calculators work out squeeze across nominal, minimum and maximum conditions directly from your groove and O-ring dimensions, and flag when it falls outside the recommended band.