The RMS velocity, or root mean square velocity, is a measure of the average speed of particles in a gas. The RMS velocity formula is v(RMS) = (3RT/M)^(1/2).
In the formula, R is the ideal gas constant (approximately 8.31 kg m^2 s^2 / K mol), T is the absolute temperature in Kelvin and M is the mass in kilograms of one mole of the gas. To use this formula, one must convert the molar mass of the gas, which is usually given in grams per mole, to kilograms by dividing by 1,000. As the temperature of a gas increases, the RMS velocity also increases, reflecting the fact that the molecules are moving around with greater speed.