Capillary Rise Calculator

How it is calculated

The tool uses Jurin's law with a fixed gravity of 9.81 m/s²:

h = 2 · γ · cos(θ) / (ρ · g · r)

Use SI units: γ is surface tension in N/m, θ is the contact angle in degrees (0 to 180), ρ is liquid density in kg/m³, and r is the inner radius of the tube in metres. The height comes out in metres and in millimetres. Density and radius must be above zero. When the angle is above 90° the cosine is negative and the result is negative, which means the liquid is pushed down below the outside level (as mercury is in glass), not raised.

Common mistakes

• Entering the diameter, or a radius in millimetres, instead of the radius in metres; 0.5 mm must be typed as 0.0005.
• Using surface tension in mN/m (72.8) instead of N/m (0.0728), which makes the result 1,000 times too large.
• Assuming a contact angle of 0° for every liquid and surface; a waxy or dirty tube has a much larger angle and a smaller rise.
• Being surprised by a negative height: for angles over 90°, such as mercury in glass, it indicates depression, not a mistake.
• Applying it to wide tubes; the formula assumes a narrow tube with a spherical meniscus, so large radii give unrealistic heights.