Reviews: Shore Hardness Scales Explained: A, D, C & OO Guide (1 comments)
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2025-11-26
MartinDyball
Hi,
Is there a percentage ratio for every 1 shore hardness (A scale)?
ie. a nitrile 70 shore o ring v a nitrile 90 shore o ring= 20 shore increase= 100% harder? would equate to a 5% increase per 1 shore hardness.
Hi, the Shore scale is non-linear, so a fixed percentage ratio doesn't work. In your example, a 90A O-ring is actually about 2 to 3 times stiffer than a 70A one (in terms of Young's Modulus). The stiffness ramps up exponentially, not linearly, as the number increases.
Hi, the Shore scale is non-linear, so a fixed percentage ratio doesn't work. In your example, a 90A O-ring is actually about 2 to 3 times stiffer than a 70A one (in terms of Young's Modulus). The stiffness ramps up exponentially, not linearly, as the number increases.