The Solar System is home to a remarkable range of planets, from tiny rocky worlds to massive gas giants. But just how big are these planets really? To put it into perspective, we can run some planetary simulations to see how many Earths, moons, and other celestial objects could fit inside each one.
These comparisons help us visualize the vast differences in size across our cosmic neighborhood. The numbers are bigger than most of us might imagine.
Mercury: The Smallest Planet
Mercury is the tiniest planet in the Solar System, so small that it cannot even fit a single Earth inside it. Despite this, it can hold a moon or two. For example, Mercury could almost contain two Moons or three Europas. It could also fit eight Plutos or 29 Tritanias, a moon of Uranus.
Enceladus, a tiny Saturnian moon only 500 kilometers in diameter, would require 906 copies to fill Mercury. Even as the smallest planet, Mercury shows us just how vast the larger planets truly are.
Mars: The Red Planet
Mars is roughly half the size of Earth and could fit two Mercuries inside its volume. It could also hold seven Moons or a surprisingly large number of Plutos. While smaller than Venus or Earth, Mars is still much larger than Mercury.
Thinking about how these planets compare gives a sense of scale as we move outward from the Sun. Even the Red Planet, modest as it seems, is impressive in its own right.
Venus: Earth’s Twin
Venus is almost the same size as Earth, which is why it is often called Earth’s twin. Although slightly smaller, Venus could fit five Marses inside it. It could also hold 15 Mercuries or 42 Moons, and even Ganymede, Jupiter’s massive moon. Venus highlights the scale of rocky planets before we reach the gigantic outer worlds. Its size sets the stage for the truly enormous planets that follow.
Earth
Earth itself could fit 49 Moons inside its volume. Compared to gas and ice giants, this makes our planet look modest. Yet Earth is large enough to host complex life and maintain a unique atmosphere. It also gives us a useful baseline for understanding the size of other planets. Our home planet is the standard for comparison in the Solar System.
Neptune: The Smallest Ice Giant
Neptune may be the smallest ice giant, but it is still enormous compared to rocky planets. It could hold 67 Venuses, 380 Marses, or 1,027 Mercuries. Earths? You could cram 57 inside Neptune’s volume. Even the smallest ice giant is vastly larger than Earth or Venus. Neptune shows how quickly planetary size escalates beyond the inner planets.
Uranus
Uranus is only slightly larger than Neptune, but it still dwarfs the rocky worlds. This icy giant could fit one Neptune and 63 Earths inside it. It could even hold nearly 10,000 Plutos. Uranus is a true giant of the outer Solar System, though still smaller than Saturn and Jupiter. Its immense size demonstrates the leap from ice giants to gas giants.
Saturn: The Ringed Giant
Saturn pushes planetary size to a whole new level. Twelve Uranuses could fit inside Saturn, along with slightly more Neptunes. In terms of Earths, you could fit 763 inside, as well as 890 Venuses, 13,000 Mercuries, or over 100,000 Plutos. Saturn’s iconic rings may grab attention, but the planet itself is truly mind-blowing in scale. Few planets in the Solar System can match its volume.
Jupiter: The Largest Planet
Jupiter is the ultimate heavyweight in the Solar System. It could hold an entire Saturn, or 20 Uranuses, or 22 Neptunes. When it comes to smaller rocky planets, the numbers are staggering: 1,321 Earths, over 20,000 Mercuries, and 203,000 Plutos could fit inside Jupiter.
Its sheer size dwarfs all other planets, making it the undisputed giant of our planetary neighborhood. Jupiter’s volume helps illustrate the incredible diversity of planets in our Solar System.
The Sun: The True Giant
Even Jupiter is tiny compared to the Sun. Our star could hold 988 Jupiters or 1,305,693 Earths. Thinking about that number makes the Sun’s enormity almost incomprehensible. It dominates the Solar System not only in size but in gravity and energy. The Sun is truly the king of our cosmic neighborhood.
The Solar System is full of planets of all sizes, from Mercury barely big enough to hold a few moons to Jupiter, which could swallow over a thousand Earths. The contrast in scale is a humbling reminder of the vastness of space. It also highlights the incredible diversity of worlds orbiting our Sun. Understanding these differences gives perspective on just how unique our planet really is.
