How is Young's modulus estimated from Shore A hardness?

Several empirical formulas exist. A common approximation: E ≈ 0.0981×(56+7.62336×S)/(0.137505×(254−2.54×S)) MPa, where S is Shore A hardness. This gives E from ~1 MPa at Shore 30A to ~15+ MPa at Shore 90A.

What Shore A hardness should I choose?

Shore 40-50A: Soft mounts for sensitive equipment, good isolation. Shore 55-65A: General purpose, most common. Shore 70-80A: Stiff mounts for heavy loads, less isolation. Shore 85-90A: Very stiff, minimal deflection.

What is the shape factor and why does it matter?

Shape factor S = loaded area / force-free area. For a cylinder: S = D/(4h). Higher shape factors increase effective stiffness because rubber is nearly incompressible. The compression modulus Ec = E×(1 + 2κS²), where κ depends on the rubber compound.

Can I use this for shear mounts?

This calculator assumes compression loading. For shear-loaded mounts, the shear stiffness is approximately k_shear = GA/h where G ≈ E/3 for rubber (Poisson's ratio ~0.5). Shear stiffness is typically 3-5× lower than compression stiffness.

How does temperature affect rubber mount properties?

Rubber stiffens significantly at low temperatures. Natural rubber (NR) works well from -40°C to +70°C. Neoprene (CR): -30°C to +100°C. Silicone: -60°C to +200°C. Stiffness can increase 2-5× below -20°C.

Free Engineering Tool #065

Rubber Mount Calculator

Calculate rubber vibration isolator stiffness from Shore A hardness (30–90A), mount dimensions, and static load. Determine natural frequency and static deflection.

Shore 30A–90ACompression StiffnessAuto-Calc

Results

Axial Compression Stiffness

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Young’s Modulus E (estimated)

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Natural Frequency

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Static Deflection

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Shape Factor

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Shore A to Young’s Modulus

Empirical relation (Gent, 1958):

Shape Factor

Compression Stiffness

Accounting for shape factor (rubber is nearly incompressible, κ ≈ 0.93):

Natural Frequency

Shore A	E (approx. MPa)	Typical Use
30A	~0.9	Very soft pads
40A	~1.5	Soft isolation
55A	~3.0	General purpose
70A	~6.2	Stiff mounts
90A	~18	Very stiff

⚠️ Note: Shore-to-modulus conversion is approximate. Actual stiffness depends on rubber compound, temperature, and loading conditions. Always verify with manufacturer data.

Rubber Mount Calculator — Shore Hardness to Stiffness | Vibromera

Published by Nikolai Shelkovenko on February 15, 2026 March 5, 2026

Results

Shore A to Young’s Modulus

Shape Factor

Compression Stiffness

Natural Frequency