Planet Size Comparison Tool
Use this planet size comparison tool to compare the diameter, radius, and relative size of planets and moons in our solar system.
Planet Size Comparison Result
Simple Size Visualization
Understanding Planet Sizes
Planet size is usually measured by diameter, which is the distance across a planet through its center. Comparing planet diameters helps students understand how different the worlds in our solar system really are.
The inner rocky planets are much smaller than the outer gas giants. Jupiter is so large that more than ten Earths could fit across its width.
Planet Diameter Comparison
| Planet or Moon | Approximate Diameter |
|---|---|
| Moon | 3,474 km |
| Mercury | 4,879 km |
| Mars | 6,779 km |
| Earth | 12,742 km |
| Jupiter | 139,820 km |
Size vs Gravity
A larger planet does not always mean proportionally stronger surface gravity. Gravity depends on mass, radius, and density. Saturn is much larger than Earth, but its surface gravity is not dramatically stronger because its density is low.
This is why planet size comparison is useful alongside tools like planet gravity calculators and escape velocity calculators.
Planet Size Comparison FAQ
What is the largest planet?
Jupiter is the largest planet in the solar system, with a diameter of about 139,820 km.
What is the smallest planet?
Mercury is the smallest official planet in the solar system.
Is Earth bigger than Mars?
Yes. Earth is much larger than Mars. Earth’s diameter is about 12,742 km, while Mars is about 6,779 km wide.
Is the Moon bigger than Mercury?
No. Mercury is larger than the Moon, although both are much smaller than Earth.
Does a bigger planet always have stronger gravity?
No. Gravity depends on mass and density, not size alone.