Pluto is less massive than Eris.
Eris (dwarf planet) . Eris is 27 % more massive than dwarf planet Pluto , though Pluto is slightly larger by volume . Pluto . In 2005 , Eris , a dwarf planet in the scattered disc which is 27 % more massive than Pluto , was discovered . Pluto is the largest and second-most-massive known dwarf planet in the Solar System and the ninth-largest and tenth-most-massive known object directly orbiting the Sun . It is the largest known trans-Neptunian object by volume but is less massive than Eris .