Pluto is about 1,413 miles (2274 km) in diameter. This is about 1/5 the diameter of the Earth. It is smaller than a lot of the other planets' moons, including our moon.

Pluto's mass is about 1.29 x 10²² kg; it is the least massive planet in our Solar System. Pluto is about 1/500th of the mass of the Earth. The gravity on Pluto is only 8% of the gravity on Earth. A 100-pound person on Pluto would weigh only 8 pounds.

Each day on Pluto takes 6.39 Earth days. Each year on Pluto takes 247.7 Earth years (that is, it takes 247.7 Earth years for Pluto to orbit the Sun once).

Pluto has a very eccentric orbit; that means that its distance from the sun varies a lot during its orbit around the sun. Pluto also rotates about its axis in the opposite direction from most of the other planets. Pluto's orbit is tilted from the plane of the ecliptic. This angle, its orbital inclination, is 17.15°. This is the largest inclination of any of the planets. Pluto's unusual orbit makes some scientists think that Pluto is not a regular planet, but perhaps an asteroid.

Pluto has one large moon, named Charon, that is almost as big as Pluto itself. Two minuscule moons were discovered in 2005. Charon was discovered by Jim Christy in 1978. Charon was named after the mythological demon who ferried people across the mythological river Styx into Hades.

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