Size of Planets in Order (2024)

The size of planets in our solar system varies dramatically. Let’s explore the sizes of the planets, including their radius and diameter in both kilometers and miles, and their relative sizes compared to Earth. Also, discover the impacts of the significant size difference between the inner and outer planets.

• The size of planets from smallest to largest is Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn, Jupiter.
• The dwarf planet Pluto is smaller than Mercury.
• Earth is the largest terrestrial or inner planet.

Size of the Planets

Our solar system comprises eight planets, which fall into two categories: the smaller, rocky inner planets (Mercury, Venus, Earth, and Mars) and the larger, gas giants (Jupiter, Saturn, Uranus, and Neptune). Another name for the gas giants is the Jovian planets, for their similarity to Jupiter. Pluto is a dwarf planet, but it’s also included here.

The Inner Planets

In order from the Sun, the inner planets are Mercury, Venus, Earth, and Mars:

1. Mercury – The smallest planet in our solar system, Mercury’s radius is about 2,440 km (1,516 mi), making its diameter roughly 4,880 km (3,032 mi). It is about 0.38 times the size of Earth.
2. Venus – Venus has a radius of approximately 6,052 km (3,761 mi) and a diameter of about 12,104 km (7,521 mi). It’s almost the same size as Earth, at about 0.95 times its size.
3. Earth – Our home planet has a radius of 6,371 km (3,959 mi) and a diameter of 12,742 km (7,918 mi).
4. Mars – The “Red Planet” has a radius of 3,390 km (2,106 mi) and a diameter of 6,779 km (4,212 mi), making it about 0.53 times the size of Earth.

The asteroid belt separates the inner planets and the outer planets.

The Outer Planets

In order outward from the Sun, the outer planets are Jupiter, Saturn, Uranus, and Neptune.

5. Jupiter – The largest planet, Jupiter’s radius is a staggering 69,911 km (43,441 mi), and its diameter is about 139,822 km (86,881 mi). It is 11.21 times the size of Earth. However, the diameter of the Sun is about 10 times greater than that of Jupiter. Another way of looking at it is that the Sun’s volume is around 1000 times greater than that of Jupiter.
6. Saturn – With a radius of 58,232 km (36,184 mi) and a diameter of 116,464 km (72,367 mi), Saturn is 9.14 times the size of Earth.
7. Uranus – Uranus has a radius of 25,362 km (15,759 mi) and a diameter of 50,724 km (31,518 mi). It is about 3.98 times the size of Earth.
8. Neptune – Neptune’s radius is 24,622 km (15,299 mi), and its diameter is 49,244 km (30,598 mi), making it 3.87 times the size of Earth.

Dwarf Planet

Pluto and the other dwarf planets are much smaller than the Earth and other planets.

9. Pluto – As a dwarf planet, Pluto has a radius of approximately 1,188 km (738 mi) and a diameter of 2,376 km (1,476 mi). It is about 0.18 times the size of Earth.

Comparative Table of Size of Planets

This table compares the radius, diameter, and relative size of each planet compared to Earth.

Why Are Inner Planets Smaller?

The size difference between the inner and outer planets results from their composition and formation history. The inner planets, also known as terrestrial planets, consist of heavier materials like rocks and metals. These dense materials were more prevalent in the inner regions of the solar system during its formation. Rocky planets like Earth and Mars form around stars that contain a significant concentration of metals.

On the other hand, the outer planets or gas giants consist mainly of lighter elements such as hydrogen and helium. These elements were more abundant in the outer solar system and accumulated in larger quantities, leading to the formation of significantly larger planets.

Importance of Large Gas Giants

The presence of large gas giants in our solar system, particularly Jupiter and Saturn, has significant implications for Earth. These implications range from the formation and evolution of the solar system to the ongoing stability and safety of Earth. Here are some key aspects:

• Impact on Earth’s Formation and Orbit: The immense gravity of the gas giants helped in clearing the orbits of the inner planets.
• Shielding Earth from Asteroids and Comets: Jupiter and the other gas giants act as a gravitational shield for Earth and the other inner planets. Jupiter attracts and captures a significant number of asteroids and comets that might otherwise pose a threat to Earth. This reduces the frequency of potentially catastrophic impacts on Earth, although it doesn’t eliminate the risk entirely.
• Tidal Forces and Planetary Dynamics: The gravitational pull of the gas giants exerts tidal forces within the solar system. These forces influence the orbits and rotation of other bodies, including Earth. However, due to the vast distances, the direct impact on Earth is minimal compared to the influence of the Moon and the Sun.
• Influencing the Architecture of the Solar System: The gas giants significantly influence the overall architecture of the solar system. Their positions and masses shape the distribution and dynamics of other bodies in the solar system, including the asteroid belt between Mars and Jupiter and the Kuiper Belt beyond Neptune.
• Stabilizing the Solar System: The large gas giants contribute to the overall gravitational balance of the solar system. This balance helps maintain the stability of the planetary orbits over long periods, which is essential for the long-term habitability of Earth.
• Potential for Impacting Earth’s Future: In the very long term, the interactions between the gas giants and other bodies in the solar system could have more dramatic effects. Gravitational perturbations over millions or billions of years could potentially alter Earth’s orbit, although current models suggest a relatively stable system.
• Scientific and Exploration Value: The gas giants and their moons offer significant scientific value. Studying them helps us understand planetary formation, atmospheric dynamics, and potential for life.

References

• Fischer, Debra A.; Valenti, Jeff (2005). “The Planet-Metallicity Correlation”. The Astrophysical Journal. 622 (2): 1102. doi:10.1086/428383
• Lewis, John S. (2004). Physics and Chemistry of the Solar System (2nd ed.). Academic Press. ISBN 978-0-12-446744-6.
• “Planetary Physical Parameters“. Solar System Dynamics. Jet Propulsion Laboratory.
• Wang, Ji; Fischer, Debra A. (2013). “Revealing a Universal Planet-Metallicity Correlation for Planets of Different Sizes Around Solar-Type Stars”. The Astronomical Journal. 149 (1): 14. doi:10.1088/0004-6256/149/1/14
• Whipple, Fred (1964). “The History of the Solar System”. Proceedings of the National Academy of Sciences of the United States of America. 52 (2): 565–594. doi:10.1073/pnas.52.2.565

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