Which measurement is bigger?
The recorded diameter of Earth is 1.878 times the recorded diameter of Mars. The selected measurements are 12,756 km and 6,792 km, respectively.
| Object | Metric size | Imperial size | Dimension |
|---|---|---|---|
| Earth | 12,756 km | 7,926.2 mi | diameter |
| Mars | 6,792 km | 4,220.4 mi | diameter |
What this comparison measures
Compare the equatorial diameters of Earth and Mars. A width ratio does not tell you the ratio of their volumes: that requires cubing the diameter ratio for ideal spheres.
Earth: Rounded equatorial diameter; the polar diameter is slightly smaller.
Mars: Equatorial diameter from NASA’s planet-size guide.
The drawings use the same physical scale, but are simplified illustrations. They show a selected linear dimension rather than mass, surface area or volume. The space between objects makes the comparison readable and does not represent a real-world separation.
Inspect the sources
Both measurement sources are linked below the interactive board. The individual Earth entry and Mars entry provide the selected conventions and related objects.
Change either selection to explore another pair. The full size comparison tool also lets you enter a personal height. To practise estimating rather than reading the answer first, try the daily five.