If Earth were a tennis ball
Mercury would be about the size of a grape, and Venus almost another tennis ball. Jupiter would be an exercise ball about 74 centimeters across, and the Sun a sphere a little over 7 meters wide.
Scale Guide
Solar System planets to scale
Explore the scaleThe eight planets divide sharply by size and composition: four compact rocky worlds orbit inside four much larger giants.
Shared scale
Rocky planets inside, giants outside
Shared physical scale
103,472km
The split follows the snow line in the young Solar System. Close to the Sun only rock and metal could condense, so the inner planets grew from a limited supply of solid material. Farther out, water ice joined the solids, and cores grew large enough for Jupiter and Saturn to pull in huge envelopes of hydrogen and helium before the gas disk dispersed. Uranus and Neptune captured far less gas, so heavier ices and rock make up most of their mass.
Mercury, Venus, Earth and Mars are made mainly of rock and metal. Jupiter and Saturn are mostly hydrogen and helium; Uranus and Neptune hold a much larger share of water, ammonia and methane. The asteroid belt orbits between Mars and Jupiter, but all of its asteroids together add up to only about 3% of the Moon’s mass.
Inner worlds
The rocky planets took different paths
All four have solid surfaces and interiors of silicate rock and metal. Earth and Venus are nearly the same size, yet Venus’s carbon-dioxide atmosphere presses on its surface about 90 times harder than Earth’s air. Smaller Mercury and Mars cooled faster: Mercury has almost no atmosphere, and Mars keeps only a thin one.
Outer worlds
Two gas giants, two ice giants
Jupiter and Saturn are made mostly of hydrogen and helium. Uranus and Neptune are called ice giants for what they are made of: water, ammonia and methane, which deep inside exist as hot, dense fluids. None of the four has a solid surface, and all of them have rings and many moons.
Benchmark
Next to the Sun
The Sun holds about 99.8% of the Solar System’s mass and is almost ten times wider than Jupiter. At this scale Earth shrinks to a dot, and even Jupiter is a small disc.
Scale anchors
Worth remembering
The Solar System skips a middle size
No planet in the Solar System has a diameter between Earth’s and Neptune’s, although planets of that size are common around other stars.
Earth and Venus are almost twins in diameter
Venus is about 95% of Earth’s diameter, but its surface, at around 465 °C, is hot enough to melt lead.
Uranus is wider, Neptune is heavier
Uranus is only about 3% wider than Neptune, but Neptune has about 18% more mass.
Profiles
The eight planets, one by one
Diameter, mass, composition and temperature for each planet, with image credits.
Mercury is the smallest planet in the Solar System and the closest one to the Sun. Because of its unusual spin-orbit rhythm, one Mercury solar day lasts 176 Earth days, which is longer than its 88-day year.
Visual creditMESSENGER 2008 / NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington / Public domainSource: Wikimedia Commons
Venus is the second planet from the Sun and the closest planetary match to Earth in size, but its surface conditions are radically different. A dense carbon-dioxide atmosphere drives a runaway greenhouse effect that makes Venus hotter than Mercury, even though it orbits farther from the Sun.
Earth is the largest of the four rocky planets and the only world known to host life. Liquid water has covered most of its surface for billions of years, shaping both its geology and its atmosphere.
Mars is the fourth planet from the Sun, a cold, dry desert world with a thin carbon-dioxide atmosphere. Ancient river valleys, lake beds and water-formed minerals show that its surface was once much wetter.
Visual creditRosetta 2007 / ESA & MPS for OSIRIS Team MPS / UPD / LAM / IAA / RSSD / INTA / UPM / DASP / IDA / CC BY-SA 3.0 IGOSource: Wikimedia Commons
Jupiter is the largest planet in the Solar System, with about 2.5 times the mass of all the other planets combined. It spins once in just under 10 hours, the shortest day of any planet.
Visual creditJuno 2019 / NASA / JPL-Caltech / SwRI / MSSS / Kevin M. Gill / Public domainSource: Wikimedia Commons
Saturn is the second-largest planet and the least dense, with an average density below that of water. Beneath its bright rings lies a hydrogen-helium atmosphere with fast jet streams and storms that can wrap around the whole planet.
Visual creditCassini 2008 / NASA / JPL / Space Science Institute / Public domainSource: Wikimedia Commons
Uranus is an ice giant that rotates tipped over on its side, with its spin axis tilted by about 98 degrees. That extreme tilt makes its seasons unlike any other planet’s, leaving each pole pointed toward the Sun for decades at a time during its 84-year orbit.
Neptune is the farthest planet from the Sun. Its winds are the fastest measured in the Solar System, driving methane clouds at more than 2,000 kilometers per hour.
Diameter is only one way to rank the planets. By volume, Jupiter could hold about 1,300 Earths. By mass, it equals about 318 Earths. By density the order flips: Earth is the densest planet and Saturn, less dense than water, is last.
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About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides explain selected parts of that range, while focused views filter the objects by subject.