Which planets have similar diameter?

Several planets in the solar system have relatively similar diameters, often grouped based on their type (terrestrial or gas giants). Here’s a breakdown:

Terrestrial Planets (Rocky):

1. Earth and Venus:
   • Earth: 12,742 km in diameter
   • Venus: 12,104 km in diameter
     The two are very close in size, with Venus being about 95% the size of Earth.
2. Mars and Mercury:
   • Mars: 6,779 km in diameter
   • Mercury: 4,879 km in diameter
     While Mars is larger, its diameter is closer to Mercury than to Earth or Venus.

Gas Giants:

1. Jupiter and Saturn:
   • Jupiter: 139,820 km in diameter
   • Saturn: 116,460 km in diameter
     Both are massive, with Saturn being about 83% the size of Jupiter.
2. Uranus and Neptune:
   • Uranus: 50,724 km in diameter
   • Neptune: 49,244 km in diameter
     These two ice giants are almost identical in size, differing by only about 3%.

Thus, Venus/Earth and Uranus/Neptune are the most similar in diameter.