Surface Tension Calculator
Calculate surface tension for droplets, bubbles, jets, and flat surfaces with physics formulas
Calculate Surface Tension
Single interface (liquid-air)
Diameter of the spherical droplet
Internal pressure
Surface Tension Results
Formula used: T = P × D / 4
Surface type: Single interface (liquid-air)
Category: No data - Enter values to calculate
Example: Water droplet on a surface
Physics Analysis
Example: Soap Bubble
Given Parameters
Shape: Soap bubble
Diameter: 40 mm = 0.04 m
Pressure difference: 2.5 Pa
Formula: T = P × D / 8
Calculation
T = 2.5 Pa × 0.04 m / 8
T = 0.1 Pa⋅m / 8
T = 0.0125 N/m
This is typical for soap film surface tension
Common Surface Tensions
Surface Types
💧 Droplet
Single liquid-air interface
T = P × D / 4
🫧 Bubble
Two interfaces (inner & outer)
T = P × D / 8
🚿 Jet
Cylindrical liquid stream
T = P × D / 2
📏 Flat
Rectangular container surface
T = 0.5 × F / L
Physics Tips
Surface tension decreases with temperature
Surfactants reduce surface tension
Bubbles have half the tension of droplets
Units: N/m or J/m² (equivalent)
Understanding Surface Tension
What is Surface Tension?
Surface tension is the tendency of liquid surfaces to minimize their surface area due to cohesive forces between molecules. It acts like an elastic membrane at the liquid-air interface, allowing insects to walk on water and droplets to form spherical shapes.
Physical Origin
- •Intermolecular forces create cohesion between liquid molecules
- •Surface molecules have unequal attractions (fewer neighbors)
- •Energy required to create new surface area
- •Measured as force per unit length (N/m)
Mathematical Formulas
Droplet: T = P × D / 4
Bubble: T = P × D / 8
Jet: T = P × D / 2
Flat: T = 0.5 × F / L
Key Variables
• T = Surface tension (N/m)
• P = Pressure difference (Pa)
• D = Diameter (m)
• F = Force (N)
• L = Length (m)
Applications and Examples
💧 Water Droplets
Raindrops form spheres to minimize surface energy. Surface tension of water is 0.0728 N/m at room temperature.
🫧 Soap Bubbles
Soap reduces water's surface tension from 0.073 to ~0.025 N/m, making bubbles possible with thin, stable films.
🕷️ Water Striders
Insects use surface tension to walk on water. Their legs don't break the surface tension barrier of the water.