Bulk Modulus Calculator
Solve bulk modulus, pressure increase or volume reduction for a small uniform compression, with explicit volume and pressure units.
Estimate a bulk modulus from a measured uniform compression, or use a known modulus to predict pressure increase or volume reduction. Inputs use positive compression magnitudes; the result also shows the signed volumetric strain.
How to use this tool
- Choose the unknown quantity and enter the initial positive volume.
- Use the same volume unit for initial volume and reduction.
- Enter the two required known quantities, choosing pressure and modulus units independently.
- Check that the material and pressure range justify a constant, small-deformation modulus.
Formula
K = Δp / (reduction / V₀); reduction = V₀ × Δp / K
K is bulk modulus and Δp is the increase from the reference pressure. Signed volume change is negative during compression, so the equivalent signed relation is K = −Δp / (ΔV / V₀). The returned final volume is V₀ minus the positive reduction. Zero compression with zero pressure cannot identify K.
Example
A 1 L sample loses 0.01 L under a 100 MPa pressure increase. The reduction fraction is 0.01, giving K = 100 / 0.01 = 10,000 MPa, or 10 GPa. Final volume is 0.99 L.
Frequently asked questions
Should I enter absolute pressure?
Enter the pressure increase relative to the starting state. Absolute and gauge readings can be used only after forming that difference consistently.
Does one modulus describe all temperatures?
Not necessarily. Material state, temperature and loading conditions affect bulk modulus. Gas compression also depends on the thermal process, so a constant value is only a local approximation.
Why reject a reduction equal to the initial volume?
It would predict zero final volume, outside this model. A smaller reduction is numerically permitted but is not automatically a physically valid small compression.
Sources
Last updated: 2026-10-30