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Durometer Hardness - ASTM D2240

A measure of the indentation resistance of elastomeric or soft plastic materials based on the depth of penetration of a conical indentor. Hardness values range from 0 (for full penetration) to 100 (for no penetration). Full penetration is between 2.46 and 2.54 mm (0.097 and 0.100 in) depending on the equipment used.

It is recommended that Durometer D tests be used when Durometer A results are greater than 90 and that Durometer A tests be used when Durometer D results are less than 20. Durometer A values less than 10 are inexact and are not reported.

Delayed hardness results are sometimes reported. The delay is the time (in seconds) in between application of the indentor and when the hardness is read. If a delay is not reported, the hardness value is the instantaneous hardness (within 1 second).

Durometer Use Indentor
A Used for softer materials.
D Used for harder materials.

Shown below is a hardness comparison chart. Hardness is a complex material property influenced by a variety of factors. Any conversions using this chart will be a rough estimate and should not be considered an exact conversion.

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