Bulk Modulus Calculator

What Is Bulk Modulus?

Bulk modulus measures a material's resistance to uniform compression. It relates a pressure increase to the resulting fractional volume decrease in fluids and solids.

Bulk Modulus Formula

$$K = -V \frac{\Delta P}{\Delta V}$$ $$\frac{\Delta V}{V} = -\frac{\Delta P}{K}$$

$K$ is bulk modulus, $V$ is initial volume, $\Delta P$ is pressure change, and $\Delta V$ is volume change. The minus sign ensures $K$ is positive when pressure increase compresses the material.

Compressibility

Compressibility is the reciprocal $1/K$. Water has bulk modulus near 2.2 GPa; steel is much stiffer at roughly 160 GPa. Gases have low bulk modulus because they compress easily.

Frequently Asked Questions

What is bulk modulus used for?

It describes how much a fluid or solid volume changes under hydrostatic pressure. It appears in acoustics, deep-sea engineering, and equations of state.

Why is there a minus sign in the formula?

Increasing pressure usually decreases volume, so $\Delta P$ and $\Delta V$ have opposite signs. The minus sign makes $K$ a positive stiffness value.

How is bulk modulus different from Young's modulus?

Young's modulus applies to stretching or bending along one direction. Bulk modulus applies to uniform pressure acting on all sides, changing volume without changing shape ideally.

What is the bulk modulus of water?

At room temperature, water is about 2.2 GPa (2200 MPa). It varies slightly with temperature and dissolved air.

Can I solve for volume change instead of K?

Yes. Rearrange to $\Delta V = -V \Delta P / K$ when bulk modulus and pressure change are known.

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What Is Bulk Modulus?

Bulk Modulus Formula

Compressibility

Frequently Asked Questions

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