Free · Mechanics and material properties

Compression Bulk Modulus & Volume Strain

Calculate positive bulk modulus from a pressure increase and a negative volume change, retaining signed compressive strain.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Increasing pressure by 100,000 Pa while reducing a 1 m³ volume by 0.01 m³ gives strain −0.01 and bulk modulus 10,000,000 Pa.

Bulk strain = volume change ÷ initial volume; bulk modulus = −pressure change ÷ bulk strain

Worked example

Enter these known values and leave the other values blank.

Positive pressure increase
100000 Pa
Negative volume change
-.01 m³
Initial volume
1 m³
Signed volume strain
-0.01
Bulk modulus for the entered change
10000000 Pa

Assumptions and limitations

  • Initial volume, pressure increase and bulk modulus are positive. The volume change is negative and smaller in magnitude than the original volume.
  • This finite-change estimate assumes the material response can be represented by one bulk modulus over the entered interval.
  • The bulk-strain value is a dimensionless fraction, not a percentage entry. A value of −0.01 means one percent volume reduction.

Common questions

Why is there a minus sign?

Compression has positive pressure change and negative volume strain. The minus sign makes the bulk modulus positive.

What if the volume change is zero?

A finite positive modulus cannot be determined by dividing a positive pressure change by zero strain.

References

Bookify rejects compression that leaves zero or negative final volume. Mercury pressure columns use conventional density and standard gravity, with the exact international inch. Pounds-force per square inch use the exact international pound and inch with standard gravity, replacing the rounded captured factor. One technical atmosphere is exactly one kilogram-force per square centimeter under standard gravity. The US fluid ounce uses one 128th of the exact US liquid gallon, replacing the rounded captured reciprocal factor. The US customary cup uses one sixteenth of the exact US liquid gallon, replacing the rounded captured cup volume. Bookify replaces the captured rounded US gallon with the exact 3.785411784-liter definition.

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