Surface Tension Converter
Convert surface tension, force per unit length, between newton per meter, millinewton per meter, dyne per centimeter, erg per square centimeter, pound-force per inch and other units. Pick two units, enter a value and read the result instantly.
Select two units to see the conversion factor.
Surface Tension Formula
Every surface tension unit is a force divided by a length (or, equivalently, an energy divided by an area), so each one is a fixed multiple of one reference unit, the newton per meter (N/m). To convert, multiply the value by the size of the source unit in N/m, then divide by the size of the target unit in N/m. The factors follow exact definitions: 1 dyn = 10⁻⁵ N, 1 erg = 10⁻⁷ J, 1 gf = 0.00980665 N, 1 lbf = 0.45359237 kg × 9.80665 m/s², 1 poundal = 1 lb·ft/s², 1 in = 0.0254 m.
What Is Surface Tension?
Surface tension is the tendency of a liquid surface to contract and behave like a stretched elastic film. It arises because molecules at the surface are pulled inward by their neighbours, which makes droplets round, lets small insects walk on water and drives capillary rise in thin tubes. It is measured as a force per unit length along the surface, and the SI unit is the newton per meter (N/m).
The same quantity can be read as energy per unit area: the work needed to enlarge the surface by one square meter is one joule, and 1 J/m² equals 1 N/m. That is why the CGS units dyne per centimeter (dyn/cm) and erg per square centimeter (erg/cm²) have exactly the same value: 1 erg/cm² = 1 dyn/cm = 1 mN/m.
Typical values show the scale. Water at about 20 °C has a surface tension of roughly 72 mN/m (72 dyn/cm), ethanol about 22 mN/m and mercury about 485 mN/m. Soaps and surfactants lower the surface tension of water, and the value falls as temperature rises. Surface tension is related to wetting and spreading but is not the same as viscosity or interfacial tension between two liquids, which have their own measurements.
Supported Units
This converter supports the following 8 surface tension units. The last column shows how many newtons per meter one unit equals. Note that 1 dyn/cm, 1 erg/cm² and 1 mN/m are all the same size, while 1 erg/mm² is a hundred times larger (100 mN/m).
| Unit | Symbol | Value in N/m |
|---|---|---|
| Newton per meter | N/m | 1 |
| Millinewton per meter | mN/m | 0.001 |
| Gram-force per centimeter | gf/cm | 0.980665 |
| Dyne per centimeter | dyn/cm | 0.001 |
| Erg per square centimeter | erg/cm² | 0.001 |
| Erg per square millimeter | erg/mm² | 0.1 |
| Poundal per inch | pdl/in | 5.44310844 |
| Pound-force per inch | lbf/in | 175.1268352 |
How to Use the Surface Tension Converter
- Type the surface tension in the value box. Decimals and scientific notation such as 0.0025 or 2.5e-3 are accepted.
- Choose the From unit and the To unit.
- The result appears instantly, or press Convert Now. Very large or very small results are shown in scientific notation.
- Use Swap Units to reverse the conversion, Copy Result to copy the answer, open Show this value in all units for a full list, and Clear to start again.
Step-by-step by hand
- Find the size of each unit in the common base unit (N/m): 1 dyn/cm = 0.001 N/m and 1 mN/m = 0.001 N/m.
- Divide the source size by the target size to get the conversion factor: 0.001 ÷ 0.001 = 1, so 1 dyn/cm = 1 mN/m.
- Multiply by your value: 72 dyn/cm × 1 = 72 mN/m.
Surface tension cannot be negative here, so only zero and positive numbers are accepted.
Common Surface Tension Conversions
- Water at about 20 °C: 72 dyn/cm equals 72 mN/m and 0.072 N/m.
- From SI to CGS: 0.0728 N/m equals 72.8 dyn/cm.
- Energy form: 1 erg/cm² equals 1 dyn/cm and 1 mN/m.
- Imperial units: 0.5 lbf/in equals 87.56341762 N/m.
- Gram-force: 0.2 gf/cm equals 196.133 mN/m.
- Poundal: 1 pdl/in equals 5.44310844 N/m.
- Large CGS unit: 1 erg/mm² equals 100 mN/m.
Surface Tension Conversion – Common Values
Quick reference for frequently used values
| Dyne/cm | Millinewton/m | Newton/m | Gram-force/cm | Pound-force/in |
|---|---|---|---|---|
| 1 | 1 | 0.001 | 0.001019716213 | 5.710147155e-6 |
| 10 | 10 | 0.01 | 0.01019716213 | 5.710147155e-5 |
| 22 | 22 | 0.022 | 0.02243375669 | 0.0001256232374 |
| 30 | 30 | 0.03 | 0.03059148639 | 0.0001713044146 |
| 40 | 40 | 0.04 | 0.04078864852 | 0.0002284058862 |
| 50 | 50 | 0.05 | 0.05098581065 | 0.0002855073577 |
| 72 | 72 | 0.072 | 0.07341956733 | 0.0004111305951 |
| 100 | 100 | 0.1 | 0.1019716213 | 0.0005710147155 |
| 485 | 485 | 0.485 | 0.4945623633 | 0.00276942137 |
| 1,000 | 1,000 | 1 | 1.019716213 | 0.005710147155 |
Where and Why This Conversion Is Used
- Chemistry and materials science: data tables list surface tension in mN/m, dyn/cm or N/m depending on the source.
- Printing, coatings and adhesives: wetting and adhesion depend on the surface tension of liquids and surface energy of substrates, quoted in mN/m or dyn/cm.
- Pharmaceuticals and cosmetics: surfactant performance and emulsion stability are characterised by surface tension.
- Textiles, detergents and cleaning: lowering the surface tension of water improves wetting and cleaning.
- Microfluidics and droplet physics: capillary and Bond-number calculations require SI units, so older dyn/cm data are converted.
- Teaching: physics courses move between N/m and dyn/cm when comparing measurements.
To compare with a liquid’s flow resistance use the Viscosity - Dynamic Converter. For concentration of surfactant solutions see the Concentration - Solution Converter.