⭕ O-Ring Size Calculator

O-Ring Sizing Guide

O-rings are measured by their Inside Diameter (ID) and Cross Section (CS). Selecting the correct size ensures a proper seal.

Common AS568 O-Ring Sizes

Size	ID (mm)	CS (mm)	Typical Use
006	2.90	1.78	Small fittings, valves
010	6.07	1.78	Small hydraulics
015	11.11	1.78	Medium fittings
110	9.19	2.62	Automotive seals
112	12.42	2.62	Plumbing, taps
210	12.37	3.53	Larger pipes
214	22.22	3.53	Industrial seals
220	34.52	3.53	Large cylinders

How to Measure O-Rings

• Inside Diameter (ID): Measure across the inner circle
• Cross Section (CS): Measure the thickness of the rubber
• Outside Diameter (OD): OD = ID + (2 × CS)
• Use calipers for accurate measurement
• Measure unstretched O-ring at room temperature

Groove Design Guidelines

• Static seals: Groove depth = 75-85% of CS
• Dynamic seals: Groove depth = 80-90% of CS
• Groove width: Should allow 5-15% compression
• Surface finish: Smoother for dynamic, can be rougher for static

Material Selection

• Nitrile (NBR): General purpose, oils, fuels - most common
• Viton (FKM): High temp, chemicals, aggressive fluids
• EPDM: Water, steam, acids - good for outdoor
• Silicone: Food grade, wide temperature range
• Neoprene: Weather resistant, moderate chemicals

Installation Tips

• Clean groove thoroughly before installation
• Inspect O-ring for damage - no nicks, cuts, or deformation
• Lubricate O-ring with compatible grease
• Don't stretch O-ring more than 50% during installation
• Avoid sharp edges that could damage O-ring
• Check compression is within specification (typically 10-25%)

Common Failure Causes

• Wrong size - too small causes excessive compression, too large leaks
• Incompatible material - chemical attack from fluid
• Over-compression - causes permanent set and leakage
• Under-compression - insufficient sealing force
• Installation damage - cuts, twists, pinching
• Temperature extremes - hardens or softens material