# O-rings, common metric sizes (ISO 3601)

> How do I size an O-ring groove for a 3D-printed lid?

- Category: Hardware › Magnets & seals
- Kind: Hardware
- Basis: ISO 3601; groove rules of thumb for static face seals
- Page: https://xemstudio.com/objects/o-rings-metric/ · JSON: https://xemstudio.com/api/geometry?object=o-rings-metric · Plain text: https://xemstudio.com/objects/o-rings-metric/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

## Notes

- Cross-sections (CS) are standardized: 1.0, 1.5, 1.78, 2.0, 2.4, 2.62, 3.0, 3.53 mm. Inside diameter is nearly continuous.
- Static face-seal groove: depth = 0.75 × CS, width = 1.35 × CS, so the ring is squeezed ~25% and has room to spread. Printed grooves: smooth the floor (ironing or sand) or it won't seal.

## Sizes

| cross_section_mm | groove_depth_mm | groove_width_mm |
|---|---|---|
| 1.5 | 1.1 | 2.0 |
| 1.78 | 1.35 | 2.4 |
| 2.0 | 1.5 | 2.7 |
| 2.4 | 1.8 | 3.2 |
| 2.62 | 2.0 | 3.5 |
| 3.0 | 2.25 | 4.0 |
| 3.53 | 2.65 | 4.8 |

## Where the files are

- McMaster-Carr: [O-rings (free STEP/IGES/STL per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/o-rings/) — STEP, IGES, STL, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)
- Wikipedia: [O-ring](https://en.wikipedia.org/wiki/O-ring) — web — CC BY-SA 4.0 (text)

## Questions

**What groove size for a 2 mm cross-section O-ring?**

Static face seal: 1.5 mm deep, 2.7 mm wide (0.75 × CS deep, 1.35 × CS wide, 25% squeeze). Iron or sand the groove floor on a print.

**What are the standard O-ring cross-sections?**

1.0, 1.5, 1.78, 2.0, 2.4, 2.62, 3.0 and 3.53 mm (ISO 3601). Inside diameters are nearly continuous, so pick the CS first then the ID.

## Fits with

- [Tri-clamp end cap and gasket, 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-end-cap/)
- [Schedule 40 pipe and PVC fittings, 1/2 to 2 inch](https://xemstudio.com/objects/schedule-40-pipe/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)