Shore A hardness is the single most quoted number on a silicone part drawing — but it is often the least understood. This chart maps Shore A 10 to 80 to real applications, and explains how to choose a hardness that balances feel, sealing performance and durability.
What Shore A Actually Measures
Shore A measures resistance to indentation under a standard durometer tip. A low number means soft and flexible; a high number means firmer and more resistant to compression. Silicone is typically measured on the Shore A scale because its range (roughly 10A to 80A) falls comfortably within it.
CYES SILICONE compounds and molds silicone in the Shore A 20 to 80 range, and verifies hardness per ASTM D2240 on every production lot so the finished part matches the drawing, not just the datasheet.
Silicone Shore A Hardness Chart
| Shore A | Feel & character | Typical applications |
|---|---|---|
| 10A | Extremely soft, gel-like | Cushioning inserts, comfort pads, vibration dampers |
| 20A | Very soft, highly conformable | Baby teethers, makeup sponges, soft-touch grips |
| 30A | Soft, easily compressed | Baby feeding parts, medical cushions, cosmetic applicators |
| 40A | Soft-medium, gentle seal | Kitchen lids, low-pressure seals, wearable parts |
| 50A | Medium, general purpose | Gaskets, grommets, keypads, household goods |
| 60A | Medium-firm, holds shape | O-rings, stoppers, caps, automotive seals |
| 70A | Firm, high compression resistance | Industrial seals, feet, bumpers, structural gaskets |
| 80A | Firmest standard silicone | High-load seals, connectors, industrial components |
How to Choose the Right Hardness
- Sealing on uneven surfaces → softer (40–50A) conforms better and seals with less clamp force.
- Holding shape under load → firmer (60–70A) resists extrusion and permanent deformation.
- Skin and baby contact → softer (20–40A) for comfort and gentle touch.
- Dynamic flexing → mid-range (50–60A) balances flexibility with durability.
Rule of thumb: start soft for comfort and conformance, start firm for compression resistance and dimensional stability. Our DFM review recommends a hardness based on your compression set and sealing requirements before tooling begins.
Hardness, Tolerance and Compression Set
Hardness is only one input. Compression set (how much a part permanently deforms after load) and dimensional tolerance matter just as much for a reliable seal. We machine mold cavities to ±0.01 mm and report compression set alongside hardness when a part must hold a seal over time.
For a deeper look at the full picture, see our silicone material selection guide and our advanced characterization page covering stress relaxation, compression set and low-temperature performance.