Scale Explorer

Space

How big is Neptune?

Neptune

Equatorial diameter
49,528 km 30,775 mi
Polar radius
24,341 km 15,125 mi
Mass
1.02409 × 10²⁶ kg 2.25773 × 10²⁶ lb
Volume
6.254 × 10¹³ km³ 1.5 × 10¹³ cu mi
Show
Human, Mars, Earth, Neptune drawn to the same scaleHuman: height 1.61–1.75 m (too small to see at this scale). Mars: equatorial diameter 6,792 km. Earth: equatorial diameter 12,756 km. Neptune: equatorial diameter 49,528 km.Human: 1.61–1.75 m (too small to see at this scale)Mars: 6,792 kmEarth: 12,756 kmNeptune: 49,528 kmNeptune49,528 kmEarth12,756 kmMars6,792 kmHuman1.61–1.75 m · too small to see

Human is too small to see at this scale and is marked with ▲.

Everything is drawn to the same scale, standing on the same ground line. Silhouettes are simplified outlines scaled to the measured dimension. A faded outline shows the top of a size range.

Compare Neptune with something else →

Zoom out from an average adult to Neptune

Neptune is too big to show next to an average adult in one picture, so here it is in 8 steps. Each step is drawn to its own scale and zooms out from the step before.

  1. Step 1 of 8 Human → Megalodon

    A megalodon is about 8.6–15 times as long as an average adult is tall.

    Human, Megalodon drawn to the same scaleHuman: height 1.61–1.75 m. Megalodon: maximum length (estimates) 15–24.3 m.Human: 1.61–1.75 mMegalodon: 15–24.3 mMegalodon15–24.3 mHuman1.61–1.75 m
    Step 1: Human and Megalodon at the same scale.

  2. Step 2 of 8 Megalodon → Great Pyramid of Giza

    The Great Pyramid of Giza is about 5.6–9.1 times as tall as a megalodon is long.

    Megalodon, Great Pyramid of Giza drawn to the same scaleMegalodon: maximum length (estimates) 15–24.3 m. Great Pyramid of Giza: current height ≈ 137 m.Megalodon: 15–24.3 mGreat Pyramid of Giza: ≈ 137 mGreat Pyramid of Giza≈ 137 mMegalodon15–24.3 m
    Step 2: Megalodon and Great Pyramid of Giza at the same scale.

  3. Step 3 of 8 Great Pyramid of Giza → Golden Gate Bridge

    The Golden Gate Bridge is about 20 times as long as the Great Pyramid of Giza is tall.

    Great Pyramid of Giza, Golden Gate Bridge drawn to the same scaleGreat Pyramid of Giza: current height ≈ 137 m. Golden Gate Bridge: total length 2,737 m.Great Pyramid of Giza: ≈ 137 mGolden Gate Bridge: 2,737 mGolden Gate Bridge2,737 mGreat Pyramid of Giza≈ 137 m
    Step 3: Great Pyramid of Giza and Golden Gate Bridge at the same scale.

  4. Step 4 of 8 Golden Gate Bridge → Mount Everest

    Mount Everest is about 3.2 times as tall as the Golden Gate Bridge is long.

    Golden Gate Bridge, Mount Everest drawn to the same scaleGolden Gate Bridge: total length 2,737 m. Mount Everest: height above sea level 8,848.86 m.Golden Gate Bridge: 2,737 mMount Everest: 8,848.86 mMount Everest8,848.86 mGolden Gate Bridge2,737 m
    Step 4: Golden Gate Bridge and Mount Everest at the same scale.

  5. Step 5 of 8 Mount Everest → Mauna Kea

    Mauna Kea is about 1.2 times as tall as Mount Everest.

    Mount Everest, Mauna Kea drawn to the same scaleMount Everest: height above sea level 8,848.86 m. Mauna Kea: height from ocean floor to summit ≈ 10,211 m.Mount Everest: 8,848.86 mMauna Kea: ≈ 10,211 mMauna Kea≈ 10,211 mMount Everest8,848.86 m
    Step 5: Mount Everest and Mauna Kea at the same scale.

  6. Step 6 of 8 Mauna Kea → Olympus Mons

    Olympus Mons is about 2.2–2.6 times as high as Mauna Kea is tall.

    Mauna Kea, Olympus Mons drawn to the same scaleMauna Kea: height from ocean floor to summit ≈ 10,211 m. Olympus Mons: height 22–27 km.Mauna Kea: ≈ 10,211 mOlympus Mons: 22–27 kmOlympus Mons22–27 kmMauna Kea≈ 10,211 m
    Step 6: Mauna Kea and Olympus Mons at the same scale.

  7. Step 7 of 8 Olympus Mons → Mars

    Mars is about 250–310 times as wide as Olympus Mons is high.

    Olympus Mons, Mars drawn to the same scaleOlympus Mons: height 22–27 km. Mars: equatorial diameter 6,792 km.Olympus Mons: 22–27 kmMars: 6,792 kmMars6,792 kmOlympus Mons22–27 km
    Step 7: Olympus Mons and Mars at the same scale.

  8. Step 8 of 8 Mars → Neptune

    Neptune is about 7.3 times as wide as Mars.

    Mars, Neptune drawn to the same scaleMars: equatorial diameter 6,792 km. Neptune: equatorial diameter 49,528 km.Mars: 6,792 kmNeptune: 49,528 kmNeptune49,528 kmMars6,792 km
    Step 8: Mars and Neptune at the same scale.

Dimensions

MeasurementMetricImperialNotesSource
Equatorial diameter 49,528 km 30,775 mi Diameter at the equator, at the 1-bar pressure level [1] [3]
Polar radius 24,341 km 15,125 mi Centre to pole at the 1-bar level (equatorial radius is 24,764 km) [2]
Mass 1.02409 × 10²⁶ kg 2.25773 × 10²⁶ lb Total mass; source states 102.409 x 10^24 kg [2]
Volume 6.254 × 10¹³ km³ 1.5 × 10¹³ cu mi Source states 6,254 x 10^10 km3 [2]

About Neptune

Neptune is the eighth and farthest planet from the Sun, an ice giant slightly smaller than Uranus but more massive. Its equatorial diameter is 49,528 km, about four times Earth's. It was found in 1846 from mathematical predictions of where an unseen planet should be.

  • NASA gives Neptune an equatorial diameter of 49,528 km (30,775 miles), about four times wider than Earth. [3]
  • If Earth were the size of a nickel, Neptune would be about as big as a baseball. [3]
  • Neptune was discovered on 23 September 1846 by Johann Gottfried Galle, based on predictions by John Couch Adams and Urbain Le Verrier. [2]
  • Wind speeds on Neptune reach up to 580 m/s. [2]

How many fit?

  • ≈ 29 million × Human · height lined up end to end match the Neptune · equatorial diameter
  • ≈ 1.2 × 10²⁴ × Human · body mass on the scales weigh as much as Neptune · mass
  • ≈ 14 × Moon · diameter lined up end to end match the Neptune · equatorial diameter
  • ≈ 1,400 × Moon · mass on the scales weigh as much as Neptune · mass
  • ≈ 2,800 × Moon · volume packed inside, by volume fill Neptune · volume

Counts divide one sourced figure by another. "End to end" uses each object's main measurement; weight and volume rows appear only when both figures are sourced.

How it compares

Factors compare the equatorial diameter of Neptune with each object’s own main measurement (height for a human). Where a size varies, the factor is given as a range.

Notes on these figures

  • Radii are measured at the 1-bar pressure level, since Neptune has no solid surface.
  • Neptune is slightly smaller than Uranus in diameter but has more mass (102.409 vs 86.811 x 10^24 kg).

Sources

  1. NASA Space Science Data Coordinated Archive, Planetary Fact Sheet - Metric. Accessed 25 September 2026.
  2. NASA Space Science Data Coordinated Archive, Neptune Fact Sheet. Accessed 25 September 2026.
  3. NASA Science, Neptune: Facts. Accessed 25 September 2026.

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