Calculate groove width, depth, squeeze, and stretch for any o-ring size. Pick a standard AS568 dash number or enter a custom cross-section. Works for static and dynamic seals.
Calculate Your Groove Dimensions
Pick an AS568 dash number from the list. Or type in your own cross-section and ID. Then choose your seal type and hit Calculate.
or enter custom
The thickness of the o-ring cord
The inside diameter of the o-ring
Static seals do not move. Dynamic seals have sliding or rotating parts.
Results
Pick a size and hit Calculate to see your groove dimensions.
O-Ring ID--
O-Ring CS--
Groove Width--
Groove Depth--
Groove Diameter (bore/OD)--
Squeeze %--
Stretch %--
Groove Width Tolerance--
Groove Depth Tolerance--
AS568 O-Ring Groove Reference Table
Common AS568 sizes with groove dimensions for a static face seal. All values are in inches.
Showing 45 of 45 sizes
Dash Number ▲
O-Ring ID (in) ▲
Cross-Section (in) ▲
Groove Width (in) ▲
Groove Depth (in) ▲
Squeeze % ▲
-006
0.114
0.070
0.105
0.056
20.0
-007
0.145
0.070
0.105
0.056
20.0
-008
0.176
0.070
0.105
0.056
20.0
-009
0.208
0.070
0.105
0.056
20.0
-010
0.239
0.070
0.105
0.056
20.0
-011
0.301
0.070
0.105
0.056
20.0
-012
0.364
0.070
0.105
0.056
20.0
-013
0.426
0.070
0.105
0.056
20.0
-014
0.489
0.070
0.105
0.056
20.0
-015
0.551
0.070
0.105
0.056
20.0
-016
0.614
0.070
0.105
0.056
20.0
-017
0.676
0.070
0.105
0.056
20.0
-018
0.739
0.070
0.105
0.056
20.0
-019
0.801
0.070
0.105
0.056
20.0
-020
0.864
0.070
0.105
0.056
20.0
-021
0.926
0.070
0.105
0.056
20.0
-022
0.989
0.070
0.105
0.056
20.0
-023
1.051
0.070
0.105
0.056
20.0
-024
1.114
0.070
0.105
0.056
20.0
-025
1.176
0.070
0.105
0.056
20.0
-026
1.239
0.070
0.105
0.056
20.0
-027
1.301
0.070
0.105
0.056
20.0
-028
1.364
0.070
0.105
0.056
20.0
-029
0.114
0.103
0.155
0.082
20.4
-030
0.176
0.103
0.155
0.082
20.4
-031
0.239
0.103
0.155
0.082
20.4
-032
0.301
0.103
0.155
0.082
20.4
-033
0.364
0.103
0.155
0.082
20.4
-034
0.426
0.103
0.155
0.082
20.4
-035
0.489
0.103
0.155
0.082
20.4
-036
0.551
0.103
0.155
0.082
20.4
-037
0.614
0.103
0.155
0.082
20.4
-038
0.676
0.103
0.155
0.082
20.4
-039
0.739
0.103
0.155
0.082
20.4
-040
0.801
0.103
0.155
0.082
20.4
-041
0.864
0.103
0.155
0.082
20.4
-042
0.926
0.103
0.155
0.082
20.4
-043
0.989
0.103
0.155
0.082
20.4
-044
1.051
0.103
0.155
0.082
20.4
-045
1.114
0.103
0.155
0.082
20.4
-046
1.176
0.103
0.155
0.082
20.4
-047
1.239
0.103
0.155
0.082
20.4
-048
1.301
0.103
0.155
0.082
20.4
-049
1.364
0.103
0.155
0.082
20.4
-050
1.426
0.103
0.155
0.082
20.4
No sizes match your search. Try a different dash number.
Gland Design Notes
Groove surface finish should be Ra 16 to 32 microinches. A smoother finish helps the seal work better.
Break all edges on the groove. Use a 0.005" to 0.015" chamfer or radius. Sharp corners can cut the o-ring.
Static seals need 15% to 25% squeeze on the cross-section. Dynamic seals need 8% to 15%.
Groove width should be about 1.5 times the cross-section for static seals. Use 1.25 times for dynamic seals.
Keep stretch between 1% and 5% for static seals. Use 2% to 5% for dynamic seals.
Leave enough room in the groove for the o-ring to move. The o-ring should fill 70% to 85% of the groove volume.
These values are starting points. Always check your material data sheet and test the seal before production.
Need O-ring grooves machined?
Upload your CAD file for an instant quote. Free DFM review included with every order.
Static seals need 15% to 25% squeeze. Dynamic seals need 8% to 15%. Squeeze is how much the groove compresses the o-ring cross-section. Too much squeeze wears the o-ring out fast. Too little squeeze lets fluid leak past the seal. Start near 20% for most static jobs.
What is the right groove width for an o-ring?
For a static seal, make the groove width about 1.5 times the o-ring cross-section. For a dynamic seal, use about 1.25 times the cross-section. The extra space lets the o-ring move and fill the groove when pressure pushes on it. If the groove is too tight, the o-ring can extrude and fail.
What surface finish does an o-ring groove need?
The groove should have a finish between Ra 16 and Ra 32 microinches. A smoother finish gives a better seal. All sharp edges must be broken with a small chamfer or radius. Sharp corners can nick or cut the o-ring when you put the parts together. This is one of the top causes of seal failure.
What is the difference between a face seal and a radial seal?
A face seal squeezes the o-ring between two flat surfaces. Think of a lid pressing down on a groove. A radial seal squeezes the o-ring between a round shaft and a bore. Face seals are simple to design and easy to put together. Radial seals work better when parts slide or rotate, like pistons and rods.
What is the standard o-ring groove tolerance?
For static face seals, groove width tolerance is typically ±0.002″ and groove depth tolerance is ±0.001″. Dynamic seals require tighter tolerances: ±0.001″ on depth to control squeeze precisely. Surface finish in the groove should be Ra 16–32 µin to prevent o-ring extrusion and wear.
What material is best for o-ring grooves in CNC machining?
Aluminum 6061-T6 is the most common groove material for lightweight applications. For high-pressure or corrosive environments, use 303 stainless steel or 316 stainless steel. The groove walls must be smooth and burr-free — any sharp edges will cut the o-ring during installation.
How do I calculate o-ring squeeze percentage?
Squeeze % = ((cross-section diameter − groove depth) / cross-section diameter) × 100. For a 0.139″ cross-section o-ring in a 0.118″ deep groove: ((0.139 − 0.118) / 0.139) × 100 = 15.1% squeeze. Target 15–25% for static seals, 8–15% for dynamic seals.
What is gland fill percentage and why does it matter?
Gland fill is the percentage of the groove volume occupied by the o-ring. Typical target is 75–90%. Under-filled grooves (below 70%) allow o-ring extrusion under pressure. Over-filled grooves (above 90%) can cause spiral twist and seal failure. Use the calculator’s output to verify your groove dimensions achieve the target fill.
