Calculate gravitational weight force from mass and local gravitational acceleration (W = mg), with planet presets for Earth, Moon, Mars, and more.
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Weight force
686.466 N
Weight (N)
686.4655
Mass (kg)
70.0000
Gravity (m/s²)
9.80665
Weight (kgf)
70.0000
Also in Physics
Science — Physics
Weight is the gravitational force exerted on a mass: W = mg. Unlike mass, weight depends on local gravitational acceleration. On Earth, a 70 kg person weighs approximately 686 N. On the Moon (g ≈ 1.62 m/s²), the same person weighs only 113 N — about one-sixth as much.
Newton's second law gives force as F = ma. When the acceleration is gravitational (g), the resulting force is weight: W = mg. Standard Earth gravity is defined as exactly 9.80665 m/s² by international convention. Local gravity varies by latitude and altitude — near the equator at sea level it is about 9.78 m/s², and near the poles it reaches 9.83 m/s².
Gravitational acceleration varies dramatically across the solar system: Moon (1.62 m/s²), Mars (3.72 m/s²), Venus (8.87 m/s²), Jupiter (24.79 m/s²), and the Sun's surface (274 m/s²). The calculator includes presets for each, making it easy to compare how the same mass feels in different gravitational environments.
Frequently asked questions
A newton (N) is the SI unit of force. One kilogram-force (kgf) is the force exerted by one kilogram of mass under standard Earth gravity, equal to 9.80665 N. Everyday scales often read in kgf, which is why a 1 kg mass "weighs" 1 kg on a spring scale at Earth's surface.
Earth is slightly oblate (wider at the equator), so the equator is farther from Earth's centre. Gravitational force decreases with distance, and centrifugal acceleration from Earth's rotation also reduces effective gravity at the equator. The combined effect is about 0.5% difference in weight between poles and equator.
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