SURFACE SCIENCE TOOLS

Contact Angle to Surface Energy Calculator

Use your measured contact angles to calculate surface free energy with OWRK or Fowkes, or critical surface tension with Zisman. Works with measurements from any goniometer.

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Gurdeep-Saini-Photo
Written by
Gurdeep Singh Saini
Holds a BASc in Mechanical Engineering from Ryerson University (now Toronto Metropolitan University) and an MASc from York University. He develops the automatic edge and baseline detection behind the Dropometer's analysis.
COO at Droplet Lab
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alidad
Reviewed by
Dr Alidad Amirfazli
Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.
Scientific Advisor & Co-founder
Read More
Gurdeep-Saini-Photo
Written By

Gurdeep Singh Saini

COO at Droplet Lab

Holds a BASc in Mechanical Engineering from Ryerson University (now Toronto Metropolitan University) and an MASc from York University. He develops the automatic edge and baseline detection behind the Dropometer's analysis.

alidad
Reviewed By

Dr Alidad Amirfazli

Scientific Advisor & Co-founder

Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop

Choose a calculation method

Measured contact angles

Choose a method and enter angles measured on the same specimen under the same conditions. Fields marked * are required. Your measurements stay in your browser.

OWRK

Liquid values are approximate reference values at 20–25 °C, in mN/m. Confirm them against the liquid table used by your laboratory; edit the values below when needed.

Reference liquid values

Liquid values are approximate reference values at 20–25 °C, in mN/m. Confirm them against the liquid table used by your laboratory; edit the values below when needed.

LiquidTotal (mN/m)Dispersive (mN/m)Polar (mN/m)
Water72.821.851
Diiodomethane50.850.80
Ethylene glycol482919
Glycerol643430
Formamide583919
1-Bromonaphthalene44.644.60
Hexadecane27.527.50

How the calculation works

OWRK fits a geometric-mean model to all liquids simultaneously. Fowkes uses a nonpolar reference to solve the dispersive component first, then uses polar liquids to estimate the polar component. Zisman fits cos(θ) against liquid surface tension and extrapolates to cos(θ) = 1.

γL(1 + cos θ) = 2√(γSᵈ γLᵈ) + 2√(γSᵖ γLᵖ)

Zisman critical surface tension is a wettability measure, not a polar/dispersive surface-energy split. Three or more liquids from a suitable chemical series help assess the fit. Two points alone cannot assess fit quality.

Scientific references

  1. Owens, D. K., and Wendt, R. C. (1969). Estimation of the surface free energy of polymers. Journal of Applied Polymer Science, 13(8), 1741–1747.
  2. Fowkes, F. M. (1964). Attractive forces at interfaces. Industrial & Engineering Chemistry, 56(12), 40–52.
  3. Zisman, W. A. (1964). Relation of the equilibrium contact angle to liquid and solid constitution. Advances in Chemistry, 43, 1–51.

Frequently asked questions

Can I use angles from any goniometer?

Yes. The calculation uses your measured angle and the liquid surface-tension values; it is independent of the instrument manufacturer.

Why can my data fail to produce a result?

Liquid ratios must identify the chosen model. Identical liquid ratios, invalid tensions or a negative fitted component cannot provide a physically valid result. The calculator asks you to check those inputs rather than silently flooring them to zero.

Why can OWRK and Fowkes differ?

OWRK fits all liquids together. Fowkes first fixes the dispersive contribution using a nonpolar reference and estimates the polar contribution from the remaining liquids. Measurement scatter and model assumptions can cause different results.

Is Zisman critical surface tension the same as surface free energy?

No. Zisman estimates the liquid surface tension at complete wetting. It does not resolve polar and dispersive components and should not be reported as an OWRK surface-energy result.

What does a worked example look like?

Choose OWRK and keep the default liquid values. Enter example angles of 70° for water and 40° for diiodomethane. The result is 47.04 mN/m total, 39.61 mN/m dispersive and 7.43 mN/m polar. Add ethylene glycol at 50° and the three liquid fit gives 42.36 mN/m, with an R² of 0.90 that the calculator flags for review.

What does the surface energy number tell me?

Surface free energy shows how readily a liquid such as an adhesive, ink or coating will wet your surface. As a rule of thumb, a liquid wets well when its surface tension is below the surface energy of the solid. The polar component often rises after plasma or corona treatment, so track it next to the total. Compare results only when the liquids, model and test conditions match.

Does the Dropometer calculate surface energy itself?

Yes. The Dropometer contact angle and surface energy kit calculates surface free energy with the Fowkes, Equation of State and van Oss-Good models from angles it measures on the same sample. OWRK (Owens-Wendt) and Zisman critical surface tension are not built in, so use this calculator for those two.

Want to measure these angles yourself?

See the Dropometer measure contact angles and calculate surface free energy in a 15 minute call with a Droplet Lab application specialist.

Book a 15 minute demo