Mean Free Path Calculator
💨 Gas Laws & Fluids. Use the Mean free path formula to find mean free path, temperature, molecule diameter, pressure: pick the value you want, type the others, and the answer updates as you go.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Mean free path | nm |
| Temperature | K |
| Molecule diameter | pm |
| Pressure | Pa |
Worked example
Find the mean free path when Temperature = 298 K, Molecule diameter = 370 pm, Pressure = 101330 Pa.
Using λ = RT/(√(2) π d² NA P): Mean free path = 68 nm.
Frequently asked questions
What is the formula for Mean free path?
λ = RT/(√(2) π d² NA P).
What do the letters stand for, and what units are used?
Mean free path in nm, Temperature in K, Molecule diameter in pm, Pressure in Pa.
How do you calculate mean free path?
Put the values into λ = RT/(√(2) π d² NA P). For example, with Temperature = 298 K, Molecule diameter = 370 pm, Pressure = 101330 Pa, mean free path = 68 nm.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (mean free path, temperature, molecule diameter, pressure) and fill in the others: it rearranges the formula for you.
