Surface Gravity
Calculator
Results
- Surface gravity (m/s²)
- 9.820302
- Gravity compared with Earth
- 1.001392
- Escape velocity (km/s)
- 11.186165
Astronomy results
| Surface gravity (m/s²) | 9.820302 |
| Gravity compared with Earth | 1.001392 |
| Escape velocity (km/s) | 11.186165 |
formula-map diagram
- Surface gravity (m/s²)
- 9.820302
- Gravity compared with Earth
- 1.001392
- Escape velocity (km/s)
- 11.186165
Astronomical relationship
Formula
g = G M / R²= 9.8203022933856
Note
This result is a simplified model: it applies the displayed textbook formula to the values you entered, assuming ideal spherical bodies, circular orbits, blackbody radiation and perfect optics, and ignoring atmospheric seeing, relativistic corrections beyond those stated, cosmological models and measurement uncertainty. Use published ephemerides and catalogue data for real observations.
More in Astronomy and space
See all →Frequently asked questions
How is a planet's surface gravity calculated from its mass and radius?+
Surface gravity uses g = GM/r², where G is the gravitational constant, M is the planet's mass, and r is its radius, giving an acceleration typically expressed in m/s² or as a multiple of Earth's gravity (1 g ≈ 9.81 m/s²). This is the same formula behind escape velocity and weight-on-planet calculations.
Why doesn't a more massive planet always have stronger surface gravity?+
Because gravity depends on both mass and the square of radius, a very large but low-density planet can have weaker surface gravity than a smaller, denser one. Saturn, for example, is over 95 times Earth's mass but has surface gravity only slightly above Earth's, because it's so much larger and less dense.
Why is surface gravity described as 'surface' gravity for gas giants with no solid surface?+
For gas giants, 'surface' conventionally refers to the altitude where atmospheric pressure equals 1 bar, similar to Earth's sea-level pressure, used purely as a consistent reference point. It's a defined boundary for comparison purposes, not a physical ground.
How does surface gravity relate to how heavy I would feel on another planet?+
Surface gravity directly determines your weight there, since weight equals your (unchanging) mass multiplied by the local surface gravity value. A surface gravity of 0.38 g, like on Mars, means you'd weigh 38% of your Earth weight.
Does surface gravity vary across a single planet, like at the poles versus the equator?+
Yes, slightly — a planet's rotation creates a centrifugal effect that reduces effective gravity at the equator, and most planets bulge slightly at the equator too, further reducing gravity there. On Earth, this makes surface gravity about 0.5% higher at the poles than at the equator, though the calculator typically gives a single average value.