Weight on Planets

Mass is the amount of matter in your body — measured in kilograms (kg) or pounds (lb) in colloquial use. Mass never changes, no matter where you are in the universe. Weight is the force gravity exerts on your mass — measured in Newtons (N) scientifically, though we commonly use kg or lbs to express it. Weight = Mass × g (gravitational acceleration). On Earth g = 9.81 m/s². Your 70 kg mass always stays 70 kg, but your weight in Newtons changes from planet to planet.

Mars has a surface gravity of 3.72 m/s² — about 37.9% of Earth's 9.81 m/s². Multiply your weight by 0.379 to get your Mars weight. A 70 kg (154 lb) person weighs about 26.5 kg (58.4 lbs) on Mars. This relatively lower gravity (comparable to about 38% of Earth) is one reason scientists consider Mars more hospitable than most other planets — though still far below what human bodies evolved for over billions of years on Earth.

Among the planets, Jupiter has the highest surface gravity at 24.79 m/s² — about 2.528× Earth. You'd weigh approximately 2.5× your Earth weight. However, Jupiter has no solid surface. Among solid-surface bodies: Neptune (1.12×), Venus (0.904×), Saturn (1.065×) are close to Earth. Mars (0.379×) and Mercury (0.378×) are about 38% of Earth. The Sun wins overall at 27.9× Earth gravity.

Slightly less. Venus has 90.4% of Earth's gravity (8.87 m/s²). A 70 kg person weighs about 63.3 kg on Venus. Despite being almost the same size and mass as Earth, Venus's slightly lower density gives it a marginally weaker gravitational pull. Venus is often called Earth's "twin" — similar size, similar gravity, similar rock composition. But its atmosphere is 90× denser than Earth's, surface temperature is 465°C, and clouds are sulfuric acid — quite different from home.

The Moon's surface gravity is 1.62 m/s² — about 16.5% of Earth's. Multiply your weight by 0.165 to get your Moon weight. A 70 kg person weighs just 11.6 kg on the Moon. This is why Apollo astronauts could move so freely despite wearing 90 kg spacesuits. The Moon's escape velocity is also much lower (2.38 km/s vs 11.2 km/s for Earth), meaning a baseball thrown hard enough could theoretically orbit the Moon.

Saturn is much larger than Earth but far less dense. Saturn's average density is just 0.687 g/cm³ — lighter than water. Earth's density is 5.51 g/cm³. Despite Saturn being 9.5× wider than Earth, its surface gravity (10.44 m/s²) is only about 1.065× Earth's. You'd weigh only 6.5% more on Saturn than Earth — if it had a solid surface, which it doesn't. Surface gravity depends on both mass and radius: g = GM/r². Saturn's enormous radius almost cancels out its enormous mass.

No — in 2006, the International Astronomical Union (IAU) reclassified Pluto as a "dwarf planet." This triggered significant public controversy. The IAU's definition of a planet requires the body to: (1) orbit the Sun, (2) have sufficient mass for hydrostatic equilibrium (roughly spherical shape), and (3) have "cleared the neighborhood" around its orbit. Pluto fails the third criterion, as it shares its orbital zone with many other Kuiper Belt objects. On Pluto's surface, your weight would be only 6.3% of your Earth weight — weaker than the Moon.

Yes, but "floating" is technically a result of being in freefall — constantly falling toward a gravitational body but moving fast enough sideways that you miss it. There's no true "zero gravity" in space — everywhere in the universe has some gravitational influence from nearby masses. Astronauts on the ISS experience about 88% of Earth's gravity but feel weightless because they and the station are in freefall together around Earth. True microgravity regions exist far from any massive body, but even in deep space, distant stars and galaxies exert tiny gravitational forces.

A neutron star typically has a surface gravity of about 2 × 10¹¹ m/s² — roughly 20 billion times Earth's gravity. A 70 kg person would "weigh" about 1.4 × 10¹² kg (1.4 trillion kg) on its surface. Your atoms would be flattened and you'd merge into the neutron star almost instantly. Neutron stars are the collapsed cores of massive stars — the densest visible objects in the universe. A teaspoon of neutron star material weighs about 10 million tons on Earth.

Surface gravity is calculated using Newton's law of universal gravitation: g = GM/r², where G is the gravitational constant (6.674 × 10⁻¹¹ m³/kg/s²), M is the planet's mass, and r is the radius to the surface. To find your weight on another planet: multiply your Earth weight by the ratio of that planet's surface gravity to Earth's (9.81 m/s²). Example: Mars g = 3.72 m/s². Ratio = 3.72/9.81 = 0.379. 70 kg × 0.379 = 26.5 kg on Mars.