Fluids · Sealing

O-ring Seal Calculator

Design and verify piston, rod, and axial O-ring grooves per ISO 3601 and AS568 — squeeze, gland fill, and tolerance stack-up update as you type.

Seal configuration
Choose seal type and application, then specify the O-ring and housing groove.
StaticDynamic
O-ring specification
Housing Dimensions (Nominal & Tolerance, mm)
Click lock icons to fix dimensions during auto-fill
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Operating Environment & Material
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Sample result

50 mm bore piston seal, AS568-226 NBR at 10 MPa / 80°C:

  • Nominal squeeze: ~17%
  • Gland fill: ~75%
  • Temperature & pressure within rating

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Parker O-Ring Handbook

Industry reference for seal groove design and material selection.

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About O-ring seals

Groove design, squeeze, and gland fill per ISO 3601 / Parker handbook practice

An O-ring is a toroidal elastomer gasket seated in a groove and compressed between mating parts. Correct groove geometry, squeeze, and fill percentage determine whether the seal holds static pressure, survives reciprocating motion, or fails from extrusion or over-compression.

O-ring squeeze

Percentage reduction in cross-section when installed. Typically 15–30% static, 10–20% dynamic.

Squeeze % = [(CS − gland depth) ÷ CS] × 100

Gland fill

Fraction of groove volume occupied by the O-ring. Keep below ~85% to allow thermal and chemical swell.

Fill % = (O-ring area ÷ gland area) × 100

O-ring stretch

ID increase when stretched onto a groove. Keep below ~5% to avoid CS reduction and stress.

Stretch % = [(Groove ID − O-ring ID) ÷ O-ring ID] × 100
  • Application: Static vs dynamic (reciprocating, rotating) — dynamic needs lower squeeze and finer surface finish.
  • Material: NBR, FKM, EPDM, silicone, PTFE — match fluid, temperature, and pressure rating.
  • Tolerances: Combine O-ring and housing tolerances for min squeeze and max gland fill.
  • Eccentricity: Misalignment reduces squeeze on one side — limit radial clearance and runout.
  • Surface finish: Ra targets depend on speed and pressure; smoother grooves reduce wear in dynamic service.
  • Dynamic seals need smoother finishes (lower Ra) and less squeeze than static face seals.
  • Stack bore, groove, and O-ring tolerances — worst-case min squeeze is what leaks first.
  • Backup rings become necessary when gap × pressure exceeds the elastomer extrusion limit.
  • Chemical swell increases effective CS — include volume swell % for fluid compatibility checks.
  • ISO 3601 and AS568 share similar CS steps; dash numbers differ — always verify ID and CS together.

This calculator applies standard groove guidelines for preliminary design. Critical applications require manufacturer data, prototype testing, and consideration of specific fluid compatibility, thermal cycling, and assembly practice.