Neptune
Neptune is an ice giant planet with a deep blue atmosphere, orbiting the Sun beyond Uranus.
How big is it?
49,240 km across
Mean diameter · approximate
A little perspective
About the same scale as Uranus.
Uranus: Uranus is an ice giant planet with a blue-green atmosphere, orbiting the Sun on its side.
Measurements, assumptions & sources +
Neptune
Mean-radius spherical model for Neptune; actual shape is not perfectly spherical. Gravity refers to a conventional atmospheric level, not solid ground.
NASA JPL — planetary physical parameters
The marked mean diameter is calibrated. Unmeasured illustration details are representative.
Uranus
Mean-radius spherical model for Uranus; actual shape is not perfectly spherical. Gravity refers to a conventional atmospheric level, not solid ground.
NASA JPL — planetary physical parameters
The marked mean diameter is calibrated. Unmeasured illustration details are representative.
Change your perspective
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Choose a suggestion to redraw the comparison, or open its page to learn what it is.
Why this measurement?
Why we use 49,240 km
For comparison, this page uses mean diameter. This is labelled approximate; the central value is useful for comparison, while real values or measurement solutions can vary.
Mean-radius spherical model for Neptune; actual shape is not perfectly spherical. Gravity refers to a conventional atmospheric level, not solid ground.
The marked horizontal span follows the named feature; transparent margins and unmeasured details do not alter it. How calibrated comparisons work →
Recorded properties
Neptune dimensions and measurements
| Property | Selected value | Recorded range | Basis |
|---|---|---|---|
| 49,240 km | Not recorded | approximate | |
| 24,620 km | Not recorded | approximate | |
| 154,700 km | Not recorded | derived | |
| 7.618 × 10⁹ km² | Not recorded | derived | |
| 6.253 × 10¹³ km³ | Not recorded | derived | |
| 17.15 M⊕ | Not recorded | approximate | |
| 11.15 m/s² | Not recorded | approximate | |
| 30.11 AU | Not recorded | rounded orbital anchor | |
| 19,550 km/h | Not recorded | rounded orbital anchor |
Around this scale
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These links use compatible length records, ordered around the selected value.
Sources and method
Want to check the number?
The source records and measurement method remain available for inspection.
- NASA JPL — planetary physical parametersMean radii and masses. Spherical area and volume here are derived from mean radius. This atlas rounds for scale comparison.
- NASA — Planet CompareConventional surface gravities; giant-planet values refer to an atmospheric reference level. Earth uses standard gravity, 9.80665 m/s².
- Defined examples — our methodology
More ways to see it
Curated comparisons
There’s always another scale
Follow your curiosity.
SpaceEarth12,740 kmEarth is the rocky planet on which we live and the third planet from the Sun.
SpaceMoon3,475 kmThe Moon is Earth’s natural satellite and the brightest large object in Earth’s night sky.
SpaceJupiter139,800 kmJupiter is a giant planet composed mainly of hydrogen and helium, orbiting the Sun beyond the asteroid belt.
SpaceSun1,391,000 kmThe Sun is the star at the centre of the Solar System.
SpaceUranus50,720 kmUranus is an ice giant planet with a blue-green atmosphere, orbiting the Sun on its side.
SpaceSaturn116,500 kmSaturn is a giant planet made mostly of hydrogen and helium, distinguished by its extensive ring system.
SpaceVenus12,100 kmVenus is a rocky planet orbiting the Sun, covered by thick clouds of carbon dioxide and sulphuric acid.
SpaceWhite dwarf12,000 kmA white dwarf is the dense, hot remnant core left behind after a star like the Sun has exhausted its nuclear fuel and shed its outer layers.