ONE FORMULA, ONE ANSWER
Gas Mean Free Path Calculator
Check a dilute gas mean free path in kinetic theory or vacuum experiments. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
Mean free path λ
Enter values and select Calculate.
λ = k_B T / (√2 π d² p)
Assumptions
Use d,p,T>0. Assume a dilute ideal gas of identical hard-sphere particles. Enter collision diameter, not radius. This is not a precise model of gas mixtures or real molecular interactions.
Displayed values are floating-point approximations. Measurement uncertainty and design safety factors are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
This site includes Google advertising and analytics, and Cloudflare analytics.