About this calculator
Formulas follow ISO 3601-2 (informative width / depth / squeeze ratios for static and dynamic seals). Results are design recommendations — for critical applications, consult the full standard or your material supplier.
O-ring groove calculator
Enter the O-ring inner diameter and cross-section — the tool computes the recommended ISO 3601-2 groove dimensions, including squeeze % and stretch %.
Recommended groove dimensions
- Groove width
- 3.90 mm
- Groove depth
- 2.34 mm
- Squeeze
- 22.0 %
- Corner radius
- 0.30 mm
- Chamfer angle
- 15–20 °
- Groove inner diameter
- 20.00 mm
- Stretch (ID stretch)
- 0.0 %
With a free fit (groove diameter = O-ring ID) stretch is 0 %. For a static seal keep stretch below 5 %, otherwise the cross-section thins and the squeeze drops below target.
Cross-section view
Gland fill (groove fill)
77.5 %OK
Fill is in the recommended 60–85 % band — enough room for both swell and squeeze.
Ratio of the O-ring cross-sectional area (π·(CS/2)²) to the groove cross-sectional area (width × depth). The recommended band is 60–85 %, leaving room for thermal and chemical swell. Above 90 % there is a risk of extrusion — the rubber has nowhere to expand.
Surface finish (Ra)
Maximum roughness of the sealing faces per the standard. A rougher surface damages the seal during assembly and in service.
| Face | Max Ra |
|---|---|
| Dynamic sealing face | ≤ 0.4 µmfor gas / vacuum ≤ 0.2 µm |
| Static sealing faces | ≤ 0.8 µm |
| Groove side walls | ≤ 3.2 µm |
Source: ISO 3601-2 / Parker O-Ring Handbook ORD 5700
Disclaimer
This is a design guide — for tolerance-critical work, consult the full ISO 3601-2 standard or your material supplier.
The exact dimensional tolerance bands (± tolerances on groove width, depth, and diameter by size class) are part of the paid ISO 3601-2 standard and are deliberately not reproduced here — we do not invent them. To machine a groove, obtain the full standard.
How to use it
- Enter the inner diameter. O-ring inner diameter (ID) in millimetres. The value is marked on the packaging or in the catalogue.
- Enter the cross-section. O-ring cross-section diameter (CS) in millimetres. The ISO 3601-1 A–E series are 1.80 / 2.65 / 3.55 / 5.30 / 7.00 mm and the inch AS568 uses 1.78 / 2.62 / 3.53 / 5.33 / 6.99 mm; the calculator also handles cross-sections outside those series.
- Pick the application type. Static seals (face / radial) use a narrower groove and higher squeeze. Dynamic seals (reciprocating / piston) use a deeper groove and lower squeeze to reduce friction and wear; rotary applications need a separate design.
- Read the result. Width, depth, corner radius and edge chamfer — all in millimetres. Squeeze % tells you how much the O-ring will compress.
- Verify against the standard table. For critical applications, cross-check against the full ISO 3601-2 table (Annex A for metric / Annex B for inch series).
The ISO 3601-2 groove tables cover only the standardised O-ring cross-sections of ISO 3601-1 (approx. 1.78 – 7.00 mm); outside that range the values are extrapolated and we recommend consulting an ORS / Mars technician.