J/m²
joule per square meter
Surface tensionexact by definition
The joule per square metre is exactly one newton per metre. Surface tension and surface energy are the same quantity in two dresses: force per unit length of contact line, or energy per unit area of new surface created. The energy form is how solid surface science, adhesion and fracture mechanics write it.
Watch out: The two are numerically identical for liquids and not quite interchangeable for solids, where creating new surface can involve elastic strain as well. The distinction between surface stress and surface energy in solids is real and matters at the nanoscale.
| 1 J/m² | 1,000 mN/m |