Bulk Modulus Formula

Bulk modulus is the modulus associated with volume strain. The strain equal to the change in volume divided by the original volume is called volume strain. The change in the relative volume of the object when a unit compressive or tensile stress acts on the surface of the object uniformly is called Bulk modulus. The units for the bulk modulus is the pascalThe Bulk modulus helps us understand how an object reacts when compressed from all sides equally.

Bulk modulus formula 

K = V(∆P) / ∆V


K= bulk modulus in pascal

∆P denotes the change in pressure in pascal

∆V denotes the change in volume in m3

V denotes the actual volume of the object in m3

Example 1

In ammunition testing centre the pressure is found to be 255 MPa. Calculate the change in volume of the piece of the copper piece when subjected to this pressure in percentage. The bulk modulus of copper is 1.38 x  Pa.


The pressure in the testing centre is 255 MPa.

Bulk modulus,K = V(∆P) / ∆V

Substituting the values,

 (ΔV / V) = 255×106/ 1.38×1011× 100

  Therefore, the change in volume percentage is 0.184 %




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