Chemistry
Young-Laplace Equation Calculator
Find the pressure difference across a curved liquid surface such as a bubble or droplet.
Your inputs
Change any value to update the result instantly.
Pressure difference ΔP
145.6 Pa
In kPa
0.1456 kPa
In mmHg
1.0921 mmHg
Geometry
Sphere, both radii equal
Reading
The pressure inside the curved surface is higher than outside; the smaller the radius, the bigger the jump
Water at 20 °C has a surface tension near 72.8 mN/m. A soap bubble has two liquid-air surfaces, which is why its pressure jump is double that of a droplet of the same radius.
What this calculator does
Calculates the pressure jump across a curved liquid interface for droplets, bubbles and cylindrical surfaces.
What your result means
The smaller the radius of curvature, the higher the pressure inside.
Formula and working
ΔP = γ(1/R₁ + 1/R₂); sphere ΔP = 2γ/R; cylinder ΔP = γ/R
- 1
Collect the inputs
Surface tension γ = 72.8 mN/m; Interface shape = 1; Radius R₁ = 1 mm; Radius R₂ = 2 mm
- 2
Apply the formula
ΔP = γ(1/R₁ + 1/R₂); sphere ΔP = 2γ/R; cylinder ΔP = γ/R
- 3
Result
Pressure difference ΔP = 145.6 Pa
Frequently asked questions
Symbols and assumptions
- ΔP
- Pressure difference
- γ
- Surface tension
- R1, R2
- Principal radii of curvature
- • Static interface with uniform surface tension.
- • Gravity effects are negligible at this scale.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • A soap bubble has two surfaces, which doubles the pressure jump compared with a droplet.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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