Squeeze a material from all sides and its volume shrinks a little. The bulk modulus tells you how much pressure is needed: water’s is about 2.2 GPa, steel’s 160 GPa. It also sets the speed of sound in fluids.
How to use the Bulk Modulus Calculator
- Pressure change ΔP
- Initial volume V₀
- Volume decrease ΔV
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the pressure increase, the initial volume and the decrease in volume.
Inputs explained
| Field | What to enter |
|---|---|
| Pressure change ΔP | Units: MPa, kPa, bar, atm, psi, GPa |
| Initial volume V₀ | Units: L, mL, m³, US gal, ft³ |
| Volume decrease ΔV | Units: mL, L, cm³, m³ |
What each result means
- Volumetric strain ΔV/V₀ = [Volume decrease ΔV]÷[Initial volume V₀]
- Bulk modulus K = [Pressure change ΔP]÷([Volume decrease ΔV]÷[Initial volume V₀])÷1e9
- Compressibility β = 1÷([Bulk modulus K]×1e9)
Example values
How the main result changes when Pressure change ΔP changes and everything else stays at the example values above:
| Pressure change ΔP (MPa) | Bulk modulus K (GPa) |
|---|---|
| 5 | 1.1111 |
| 7.5 | 1.6667 |
| 10 | 2.2222 |
| 12.5 | 2.7778 |
| 15 | 3.3333 |
| 20 | 4.4444 |
Formula
K = −ΔP / (ΔV/V₀), compressibility β = 1/K
Worked example
Inputs — Pressure change ΔP: 10 MPa; Initial volume V₀: 1 L; Volume decrease ΔV: 4.5 mL.
Results — Volumetric strain ΔV/V₀ = 0.0045; Bulk modulus K = 2.22222 GPa; Compressibility β = 4.5000e-10 Pa⁻¹.
Key terms
- Volumetric strain
- Relative change in volume.
Frequently asked questions
What is the bulk modulus of water?
About 2.2 GPa.
Why is the sign negative in the formula?
Pressure increases make the volume decrease.
What is compressibility?
The reciprocal of the bulk modulus.
How does bulk modulus relate to sound speed?
In a fluid, c = √(K/ρ).