The masses of the galaxies are found from the orbital motion of their stars. Stars that are in a more massive galaxy will orbit faster those in a lower mass galaxy because the gravity force of massive galaxy will cause longer accelerations. For spiral galaxies the rotation curve is used to measure their masses. The rotation curve shows how orbital speeds in the galaxy depend on their distance from the galaxy's center. The orbital speed is found from the Doppler shifts of the 21cm line radiation from the atomic hydrogen gas. The formula is center=(orbital speed)squared x ( distance from the center)/G. The angular distance of the piece of the disk from the center is measured, but to use the enclosed mass formula, the piece of the disks actual linear distance from the center must be found. For the elliptical galaxies the width of the absorption lines from all of the stars blended together is used to measure the mass of elliptical galaxies. The width of the absorption lines depends on the spread of the distribution of the velocities---the velocity disperion. The formula is mass= k x (velocity dispersion)squared x ( the distance the stars are from the galaxy center)G, k is a factor that depends on the shape of the galaxy and the angle the galaxy and the angle the galaxy is from Earth.