Scale Comparison

Earth vs Neptune, to scale

Neptune is the outermost major planet, but distance is not the point here. On a true diameter scale, the important fact is that even the more compact giant planets still tower over Earth's familiar rocky standard.

Shared physical scale
27,594km
Earth12,742 km
Neptune49,528 km

Scale insight

Neptune's diameter is about 3.9 times Earth's.

Neptune helps show that giant-planet scale does not disappear once you move past Jupiter and Saturn. It belongs to a different branch of planet formation, yet it still occupies a much larger physical frame than Earth.

That makes the comparison valuable as a boundary marker. Even the more compact giant planets remain far outside the terrestrial regime, both in size and in the kind of planetary structure they represent.

Objects

Open each object in context

Planets

Earth

12,742 kmdiameter

Earth is the rocky planet on which we live and the most familiar anchor for planetary scale. It remains the only world known to host life, with long-lived surface oceans that have shaped both its geology and its atmosphere.

Object class
Terrestrial planet
Composition
Silicate rock and iron core
Temperature
~288 K mean surface
Estimated age
~4.54 billion years
Host
Sun
Visual creditNASA / Apollo 17 crew / Public domainSource: Wikimedia Commons
Planets

Neptune

49,528 kmdiameter

Neptune is the outermost giant planet in the Solar System. It is the windiest world known, with methane-cloud systems racing through its atmosphere at speeds above 2,000 kilometers per hour.

Object class
Ice giant planet
Mass
~17 Earth masses
Host
Sun
Estimated age
~4.5 billion years
Composition
Hydrogen, helium, water-ammonia-methane ices
Temperature
~59 K cloud tops
Visual creditNASA / Voyager 2 / PDS / OPUS / Ardenau4 / CC0 1.0Source: Wikimedia Commons

Between the smallest and the largest, perspective is everything.

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 turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.

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