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Surface Tension for Films, Drops and Jets

Calculate surface tension for films, drops and jets with local equations, selectable units and supported inverse relationships.

  • Formula & worked example
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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.

Private by default

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

Formula and method

Tension drop = 0.5; Force drop = 0.0031415927. Values use the worked example unit selections.

γfilm = F/(2ℓ); γdrop = Δp d/4; γbubble = Δp d/8; γjet = Δp d/2

Worked example

Enter these known values and leave the other values blank.

Shape
Droplet
Diameter of droplet (D)
2 mm
Pressure inside droplet (P)
0.001 MPa
Force due to surface tension (F)
0.0031416 N
Surface tension (T_drop)
0.5 N/m

Assumptions and limitations

  • An ideal flat film has two surfaces; a droplet has one interface; a hollow soap bubble has two. The jet model is cylindrical. Pressure means inside-minus-outside excess pressure and geometry must match the selected mode.
  • Unit selectors convert known physical quantities. Leave a supported unknown blank; derived inverse branches are limited by the stated model and available captured equations.

Common questions

What does this calculation assume?

An ideal flat film has two surfaces; a droplet has one interface; a hollow soap bubble has two. The jet model is cylindrical. Pressure means inside-minus-outside excess pressure and geometry must match the selected mode.

Can I solve for an input?

Where the captured model supplies an inverse, leave that quantity blank and enter the remaining known quantities. A positive square-root or principal trigonometric inverse may represent only one of multiple mathematical branches.

Which unit should I use for the worked example?

The example uses the initial metric unit selection beside each field. Change a unit using its selector to convert the same known quantity; switching a unit does not change the underlying physical value.

References

Captured local equations and controls are preserved with explicit physical-domain and exact-unit corrections where disclosed. Diagram explanations and guides are authored for Bookify. Validation covers the recorded cases and does not certify every real-world application. The pound-force uses the exact international pound and standard gravity instead of the rounded captured factor. Pound-force stiffness and damping units use the exact international pound and length with standard gravity. Pounds-force per square inch use the exact international pound and inch with standard gravity, replacing the rounded captured factor. Pounds-force per square foot use the exact international pound and foot with standard gravity.

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