What is gravitational field strength?

Gravitational field strength (g) is the gravitational force experienced per unit mass at a point in space, measured in m/s² (or equivalently N/kg). At Earth's surface it is approximately 9.81 m/s².

What formula does this calculator use?

The calculator uses Newton's law of universal gravitation: g = GM/r², where G = 6.674 × 10⁻¹¹ N·m²/kg², M is the mass of the body in kg, and r is the distance from its center in meters.

How does distance affect gravitational field strength?

Gravitational field strength follows an inverse-square law: doubling the distance reduces g to one quarter of its original value. At twice the Earth's radius, surface gravity drops to about 2.45 m/s².

Why is g different on different planets?

Each planet has a different mass and radius. Larger mass increases g, while larger radius decreases it. Jupiter's enormous mass gives it a surface gravity of about 24.8 m/s², while Mars's smaller mass yields only 3.73 m/s².

What is the difference between g and G?

G (capital) is the universal gravitational constant, 6.674 × 10⁻¹¹ N·m²/kg², a fixed number of nature. g (lowercase) is the local gravitational field strength, which varies with location and the body you are near.

Can I use this for orbit calculations?

Yes. Enter the planet's mass and set the distance to the orbital radius (planet radius + altitude). The result is the gravitational acceleration experienced by an orbiting satellite at that altitude.

Gravitational Field Strength Calculator

Calculate the gravitational field strength at any distance from a planet or star using g = GM/r².

Inputs

Celestial Body Preset

Mass of Body (kg) e.g. 5.972e24

Distance from Center (m) e.g. 6.371e6

Formula: g = GM / r² · G = 6.674 × 10⁻¹¹ N·m²/kg²

Select a preset or enter values to calculate gravitational field strength.

Surface Gravity Comparison

Body	g (m/s²)	vs Earth

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Summary

Gravitational field strength (g) measures the gravitational force per unit mass at a given point in space, expressed in m/s². It is calculated using Newton's law of gravitation: g = GM/r², where G is the gravitational constant (6.674 × 10⁻¹¹ N·m²/kg²), M is the mass of the body, and r is the distance from the center of that body. This tool lets you compute g for any custom mass and distance, or choose from built-in presets for the Sun, Earth, Moon, Mars, Jupiter, and other well-known bodies.

How it works

Select a celestial body preset or choose "Custom" to enter your own values.
Enter the mass of the body in kilograms (or use the preset value).
Enter the distance from the center of the body in meters.
The gravitational field strength g (m/s²) is calculated instantly using g = GM/r².
Compare results across multiple bodies using the preset buttons.

Use cases

Calculate surface gravity for any planet or moon.
Determine gravity at orbital altitude above Earth or another body.
Solve physics homework problems involving gravitational fields.
Explore how gravity weakens with distance (inverse-square law).
Compare gravitational environments for space mission planning.
Verify textbook values for planetary surface gravities.
Study the effect of mass on gravitational field strength.
Calculate g for hypothetical or custom-mass bodies.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu