Surface Tension Converter
Convert surface tension between N/m, mN/m, dyne/cm, and lbf/ft.
Water is 72 mN/m.
Used in fluid mechanics, detergent formulation, and coating applications.
Type in any field — the others update instantly.
Surface tension is the inward pull that holds a liquid’s surface together. It’s why water beads up, why droplets pull themselves round, and why some insects can stand on a pond. Physically it’s the energy needed to grow the surface by one unit of area, so newtons per meter and joules per square meter describe the same quantity. The SI unit is the newton per meter (N/m), though values are small enough that millinewtons per meter is the practical scale.
Key conversions:
- 1 N/m = 1,000 mN/m (millinewtons per meter)
- 1 dyne/cm = 0.001 N/m = 1 mN/m
- 1 lbf/ft = 14.594 N/m
The dyne per centimeter is the old cgs unit and still rules chemistry and coatings work, where it happens to equal the mN/m exactly.
Where common liquids land:
- Water at 20°C: about 72.8 mN/m
- Ethanol: about 22 mN/m
- Mercury: about 485 mN/m
Water’s high value is exactly why it won’t wet a greasy surface on its own. The entire job of soap and detergent is to crash that number down toward ethanol territory so water can creep into fabric and grime.
Two cautions when you measure it. Surface tension falls as temperature rises, and even a trace of oil or surfactant can swing a reading hard. A clean instrument matters more here than in almost any other measurement.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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