By Zencalcy Editorial TeamLast reviewed About us
The bulk modulus measures a material's resistance to uniform compression. It is defined as the ratio of the infinitesimal pressure increase to the resulting relative volume change.
Modulus for uniform compression.
K = -ΔP / (ΔV / V₀)
ΔP is the pressure increase, ΔV the volume change and V₀ the original volume. The minus sign ensures K is positive when compression (ΔV < 0) is applied.
| Symbol | Meaning |
|---|---|
| K | Bulk modulus. |
| ΔP | Pressure change. |
| ΔV / V₀ | Volumetric strain (negative for compression). |
K = 2 GPa / 0.001 = 2 TPa, typical for diamond.
Continue with the Poisson's Ratio Calculator, Linear Thermal Expansion Calculator, or the Volumetric Thermal Expansion Calculator — or browse more materials and elasticity tools and all physics calculators.
The inverse is compressibility, measured in Pa⁻¹. Fluids have lower bulk moduli than solids.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Content updated: September 2026