Graham's Law Calculator

About this calculator

This calculator applies Graham's law of effusion: rate1 / rate2 = √(M2 / M1), where M1 and M2 are the molar masses of two gases. It shows that lighter gases effuse (or diffuse) through a small opening faster than heavier ones, with the rate ratio equal to the inverse square root of the molar mass ratio.

Chemistry students and instructors use it in classic effusion experiments (like comparing HCl and NH3 diffusion in a tube) and in problems involving isotope separation, where the same principle historically helped enrich uranium-235 from uranium-238 by exploiting their small molar mass difference as UF6 gas. Enter the two molar masses to get the rate ratio.