Scale Explorer

Space

How big is the Andromeda Galaxy?

Andromeda Galaxy · Messier 31

Diameter (estimated)
220,000–260,000 light-years 220,000–260,000 light-years range
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Human, Milky Way galaxy, Andromeda Galaxy drawn to the same scaleHuman: height 1.61–1.75 m (too small to see at this scale). Milky Way galaxy: disc diameter (estimated) 100,000–200,000 light-years. Andromeda Galaxy: diameter (estimated) 220,000–260,000 light-years.Human: 1.61–1.75 m (too small to see at this scale)Milky Way galaxy: 100,000–200,000 light-yearsAndromeda Galaxy: 220,000–260,000 light-yearsAndromeda Galaxy220,000–260,000 light-yearsMilky Way galaxy100,000–200,000 light-yearsHuman1.61–1.75 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 Andromeda Galaxy with something else →

Zoom out from an average adult to the Andromeda Galaxy

The Andromeda Galaxy is too big to show next to an average adult in one picture, so here it is in 12 steps. Each step is drawn to its own scale and zooms out from the step before.

  1. Step 1 of 12 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 12 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 12 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 12 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 12 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 12 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 12 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 12 Mars → Uranus

    Uranus is about 7.5 times as wide as Mars.

    Mars, Uranus drawn to the same scaleMars: equatorial diameter 6,792 km. Uranus: equatorial diameter 51,118 km.Mars: 6,792 kmUranus: 51,118 kmUranus51,118 kmMars6,792 km
    Step 8: Mars and Uranus at the same scale.

  9. Step 9 of 12 Uranus → Saturn

    Saturn is about 2.4 times as wide as Uranus.

    Uranus, Saturn drawn to the same scaleUranus: equatorial diameter 51,118 km. Saturn: equatorial diameter 120,536 km.Uranus: 51,118 kmSaturn: 120,536 kmSaturn120,536 kmUranus51,118 km
    Step 9: Uranus and Saturn at the same scale.

  10. Step 10 of 12 Saturn → Sun

    The Sun is about 12 times as wide as Saturn.

    Saturn, Sun drawn to the same scaleSaturn: equatorial diameter 120,536 km. Sun: diameter ≈ 1.39 million km.Saturn: 120,536 kmSun: ≈ 1.39 million kmSun≈ 1.39 million kmSaturn120,536 km
    Step 10: Saturn and Sun at the same scale.

  11. Step 11 of 12 Sun → Betelgeuse

    Betelgeuse is about 350–700 times as in radius as the Sun is wide.

    Sun, Betelgeuse drawn to the same scaleSun: diameter ≈ 1.39 million km (too small to see at this scale). Betelgeuse: radius (estimated) 700–1,400 solar radii.Sun: ≈ 1.39 million km (too small to see at this scale)Betelgeuse: 700–1,400 solar radiiBetelgeuse700–1,400 solar radiiSun≈ 1.39 million km · too small to see
    Step 11: Sun and Betelgeuse at the same scale.

  12. Step 12 of 12 Betelgeuse → Andromeda Galaxy

    The Andromeda Galaxy is about 2.1 billion–5.1 billion times as across as Betelgeuse is in radius.

    Betelgeuse, Andromeda Galaxy drawn to the same scaleBetelgeuse: radius (estimated) 700–1,400 solar radii (too small to see at this scale). Andromeda Galaxy: diameter (estimated) 220,000–260,000 light-years.Betelgeuse: 700–1,400 solar radii (too small to see at this scale)Andromeda Galaxy: 220,000–260,000 light-yearsAndromeda Galaxy220,000–260,000 light-yearsBetelgeuse700–1,400 solar radii · too small to see
    Step 12: Betelgeuse and Andromeda Galaxy at the same scale.

Dimensions

MeasurementMetricImperialNotesSource
Diameter (estimated) 220,000–260,000 light-years 220,000–260,000 light-years Estimated: 'some 220,000 light-years wide' (NASA) to 260,000 light-years for the whole galaxy/disc (NASA GALEX, NASA Space Place). Range: varies [1] [2] [3]

About the Andromeda Galaxy

The Andromeda Galaxy (M31) is the nearest large spiral galaxy to the Milky Way, about 2.5 million light-years away. NASA estimates it at roughly 220,000 to 260,000 light-years across, well over twice the commonly quoted width of our own galaxy's disc. From a dark site it is visible to the unaided eye, and its angular size is about six times that of the full Moon.

  • At about 2.5 million light-years away, Andromeda is the Milky Way's largest galactic neighbour; in NASA's Galaxy Evolution Explorer ultraviolet image the entire galaxy spans 260,000 light-years. [2]
  • NASA Space Place gives the disc of Andromeda as about 260,000 light-years, compared with about 100,000 light-years for the Milky Way's disc. [3]
  • In angular size Andromeda appears about six times the apparent diameter of the full Moon; a 2025 Hubble panorama of it needed over 600 overlapping snapshots. [4]

How many fit?

  • ≈ 1.2 × 10²¹–1.5 × 10²¹ × Human · height lined up end to end match the Andromeda Galaxy · diameter (estimated)
  • ≈ 1.8 × 10¹⁴ × Earth · equatorial diameter lined up end to end match the Andromeda Galaxy · diameter (estimated)

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

  • 1.2 × 10²¹–1.5 × 10²¹× The Andromeda Galaxy is about 1.2 × 10²¹–1.5 × 10²¹ times as across as an average adult is tall. See side by side
  • 1.8 × 10¹⁴× The Andromeda Galaxy is about 1.8 × 10¹⁴ times as across as Earth is wide. See side by side
  • 1.6 × 10¹³× The Andromeda Galaxy is about 1.6 × 10¹³ times as across as Jupiter is wide. See side by side
  • 1.9 × 10¹³× The Andromeda Galaxy is about 1.9 × 10¹³ times as across as Saturn is wide. See side by side
  • 1.6 × 10¹²× The Andromeda Galaxy is about 1.6 × 10¹² times as across as the Sun is wide. See side by side
  • 1.1–2.6× The Andromeda Galaxy is about 1.1–2.6 times as across as the Milky Way. See side by side

Factors compare the diameter (estimated) of the Andromeda Galaxy 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

  • All sizes are estimated. The galaxy has no sharp edge, and the figure depends on the wavelength and how far out the faint disc is traced.
  • No NASA or ESA page fetched gives Andromeda's mass in a unit the site supports, so mass is left out.

Sources

  1. NASA Science, Our Milky Way Galaxy: How Big is Space?. Accessed 25 September 2026.
  2. NASA, The Galaxy Next Door. Accessed 25 September 2026.
  3. NASA Space Place, The Andromeda Galaxy - Across the Spectrum (poster). Accessed 25 September 2026.
  4. NASA Science, Messier 31 (The Andromeda Galaxy). Accessed 25 September 2026.

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