Kelvin Equation Calculator

Calculate the change in vapour pressure using: $$ \ln\!\left(\frac{P}{P_0}\right) = \frac{2\gamma\,V_m}{r\,R\,T} $$

* Enter the flat surface vapour pressure $P_0$ (Pa), surface tension $\gamma$ (N/m), molar volume $V_m$ (m³/mol), radius of curvature $r$ (m), and temperature $T$ (K).

Step 1: Enter Parameters

Flat Surface Vapour Pressure, $ P_0 $ (Pa):

e.g., 101325 Pa

Surface Tension, $ \gamma $ (N/m):

e.g., 0.072 N/m for water at 20°C

Molar Volume, $ V_m $ (m³/mol):

e.g., 1.8×10⁻⁵ m³/mol (typical for water)

Radius of Curvature, $ r $ (m):

e.g., 0.0001 m

Temperature, $ T $ (K):

e.g., 298.15 K (25°C)

Step 1: Enter Parameters

Calculated Vapour Pressure