The planet Jupiter, the largest in both diameter and mass in the Solar System, weighs almost as much as 318 Earths.
You might think, then, that on Jupiter (if you could float at the tops of the clouds of Jupiter) you'd weigh 318 times as much as on Earth. That would be the case indeed if Jupiter were the same size as Earth. But it's much bigger, and the strength of a planet's gravity diminishes the farther away you get from its center of mass.
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To get the approximate gravity in Earth Gs, you need to divide the mass in Earth masses by the *square* of the radius in Earth radii. In the case of Jupiter, this comes out to about 2 and a half (Jupiter is not perfectly spherical, so its gravity varies at different points on its surface.)
The same thing happens with other giant planets, with the result that most of them have gravities not much greater than, or even less than Earth's.
The fact that surface gravity depends not just upon the mass of a planet, but also upon its size, means that an ordering of planets by mass is completely different from an ordering by gravity.
By mass (in Earths): Jupiter 318, saturn 95, Neptune 17, Uranus 14.5, Earh 1, Venus 0.8, Mars 0.1, Mercury 0.055, Moon 0.012, Pluto 0.002.
By gravity (in Gs): Jupiter 2.4-2.7, Neptune 1.12, Earth 1, Saturn 0.92-1.2, Venus 0.91, Uranus 0.89, Mercury 0.38, Mars 0.38, Moon 0.17, Pluto 0.07.
@DavidSalo I read about the moon losing its mass. Then I had a nightmare that the dinosaurs were killed by a 2nd moon that used to orbit around earth until it lost too much mass and spiraled into Earth. I love science but it makes me crazy at times!