Reference guide
How Much Squeeze Should an O-Ring Have?
A face seal takes the most squeeze: Parker's handbook puts the static maximum for most elastomers at 30 percent and calls that much often beneficial in a face seal. Whatever the percentage, the Parker handbook sets 0.007 in of absolute squeeze as the floor, because below about 0.005 in a ring takes close to 100 percent compression set.
An O-ring seals by being squeezed, and the published manufacturer guidelines set the squeeze by seal type: most for a static face seal, less for a static radial seal and least for a dynamic one. Parker's handbook sets the floor for every case: never design below 0.007 in of absolute squeeze, because below about 0.005 in the ring takes close to 100 percent compression set and stops sealing. This guide covers the published limits, the rotary case, and what temperature, swell and stretch do to the number; the groove for a given AS568 ring comes from the standard or the maker's design chart your drawing names.
Squeeze by seal type
A face seal takes the most squeeze because nothing moves and the flanges carry the load; the Parker handbook calls face seals the most tolerant gland type with the best low-temperature margin, and puts the static maximum for most elastomers at 30 percent. Rotary service is a separate design case: 0 to 11 percent by cross-section and speed (Parker Design Chart 5-4), with the ring sized 2 to 5 percent larger than the shaft, not smaller (Trelleborg).
Why the squeeze exists at all
Trelleborg lists five jobs for initial compression: achieve the initial seal, bridge production tolerances, set a defined friction force, compensate for compression set, and compensate for wear. The fourth is the one that decides where in the band to start: a compound that takes a large set has to begin higher so it still has squeeze left after the set is taken, which is why the compression set guide and this one are read together.
What changes the number
| Condition | Effect on squeeze | Published guidance |
|---|---|---|
| Fluid swell 15 to 25 percent | Raise minimum squeeze AND open the groove: on a 0.139 in axial gland Precision Associates' high-swell chart moves minimum squeeze from 0.025 to 0.030 in and widens the groove from 0.185 to 0.215 in | Precision Associates; sealing a fluid that swells the ring more than 25 percent is not practical |
| Swell in dynamic service | Keep swell near 10 percent; above that, friction problems | Parker ORD 5700 |
| Installed stretch | Over 2 to 3 percent stretch needs a gland-depth correction; over 5 percent is not recommended | Parker |
| Compression set | Start higher in the band for a compound with poor set | Trelleborg |
Squeeze and the other two gland rules
Squeeze works with gland fill and stretch. Fill the groove to 60 to 85 percent of its volume (Parker's optimum is 75 percent), checked at maximum ring against minimum groove, and keep assembled stretch inside the published limits: 0 to 2 percent on a face seal under internal pressure, 1 to 3 percent under external pressure, 2 to 8 percent on a static piston and 2 to 5 percent on a dynamic piston on Trelleborg's figures, zero on a rod. Parker does not recommend more than 5 percent; above 2 to 3 percent, correct the gland depth. The groove design guide covers fill, stretch, rotary glands and surface finish.
The ranges in this guide are the published design guidelines of the manufacturers named beside them (Parker, Trelleborg, Precision Associates and Apple Rubber), re-arranged by seal type. They are not Conquest Seal engineering recommendations: Conquest distributes seals and cuts gaskets, and does not design parts. If a drawing calls out SAE AS4716, SAE AS5857, ISO 3601-2 or MIL-G-5514, the standard governs and these ranges are context.
Sources
- Parker O-Ring Handbook ORD 5700 (2021 printing), sections 3.5 to 3.7 (stretch, squeeze and gland fill), read 2026-09-24; section 5.27 and Design Chart 5-4 (rotary O-ring seal glands, page 5-39), read 2026-10-13
- Trelleborg Sealing Solutions, O-Rings and Back-up Rings catalog (June 2024 edition), read 2026-09-06
- Precision Associates, Application Data: Seal Gland Design (2011), read 2026-09-06
- Apple Rubber Products, Seal Design Guide (Rules of Thumb; O-Ring Installation), read 2026-09-06
- SAE AS4716 and AS5857, ISO 3601-2 and MIL-G-5514: titles and scope only, from the SAE, ISO and ASSIST records read 2026-09-06
Frequently asked questions
Is more squeeze always safer?
No. Stay inside the published band for the seal type: Parker puts the static maximum for most elastomers at 30 percent, and in dynamic service more squeeze means more friction.
What is the absolute minimum squeeze?
0.007 in, per Parker's handbook; below about 0.005 in everything takes 100 percent compression set. That is an absolute figure, not a percentage, which is why small sections carry high percentages.
Does squeeze change with material?
The bands are the same for all elastomers; what changes is where in the band to start (higher for poor-set compounds and cold service) and, for silicone, the clearance allowed beside the gland, which Parker halves.
How do I check squeeze on a metric ring?
The same way; use the ISO 3601-2 housing tables if the hardware is metric, and note that ISO and the AS568 industrial convention differ slightly on static depth for the large sections. The metric O-ring sizes guide covers the size systems.
Which durometer for a given squeeze?
Durometer is chosen for pressure and clearance, not squeeze; see the durometer guide.
How does swell change the squeeze?
Precision Associates publishes two complete chart sets, one for normal swell of 0 to 15 percent and one for high swell of 15 to 25 percent. On a 2xx face-seal gland the high-swell chart raises the minimum squeeze from 0.025 to 0.030 in, makes the gland shallower and the groove wider, and no published source considers it practical to seal a liquid that swells the ring more than 25 percent.
How much stretch is allowed on the inside diameter?
Trelleborg allows a static piston gland 2 to 8 percent stretch, a dynamic piston 2 to 5 percent, and a face seal under external pressure 1 to 3 percent; rod glands are sized with no stretch. Parker does not recommend more than 5 percent; above 2 to 3 percent, correct the gland depth.
Related guides
Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution.
Send the part number and we quote it
Part number or drawing, compound if you know it, and the quantity. A Conquest representative reads every request and replies. Quotes answered within one business day. A person answers (714) 632-9830, Pacific business hours.
Request a quoteLast updated