The Moon is about 27% the width of Earth, with a diameter of 3,474 km (2,159 mi) compared to Earth's 12,742 km (7,918 mi). In terms of volume the gap is far more dramatic: the Moon holds only about 2% of Earth's volume, meaning you could pack roughly 49 Moons inside our planet. The Moon may dominate the night sky, but it is a genuinely small world held in orbit by a much larger one.
Diameter, Volume, and Mass Side by Side
The single number most people want is the diameter, and the comparison is easy to picture: line up about 3.7 Moons in a row and you would span the full width of Earth. The differences grow quickly once you move from a line to a solid sphere.
- Diameter: Moon 3,474 km vs Earth 12,742 km — the Moon is 27.3% as wide.
- Surface area: Moon 37.9 million km² vs Earth 510.1 million km² — about 7.4%.
- Volume: Moon 21.9 billion km³ — roughly 2% of Earth's, so about 49 Moons would fit inside Earth.
- Mass: Moon 7.35 × 10²² kg — only about 1.2% of Earth's mass.
This is why the Moon, despite spanning more than a quarter of Earth's diameter, is such a lightweight partner: volume and mass scale with the cube of size, so a modest difference in width becomes an enormous difference in bulk.
Making the Moon's Size Tangible
Raw figures in the billions are hard to feel, so comparing the lunar surface to places on Earth helps. The Moon's total surface area of 37.9 million km² is slightly larger than the continent of Africa (about 30.4 million km²). The entire African landmass could be laid across the Moon with room to spare.
- Russia (17.1M km²) would blanket roughly 45% of the lunar surface.
- The United States (about 9.8M km²) would cover around a quarter, so about four of them fit on the Moon.
- Australia (7.7M km²) accounts for roughly 20% of the surface.
Another way to picture it: the Moon's equatorial circumference is about 10,921 km. Driving non-stop around it at highway speed (100 km/h) would take roughly 4.5 days — yet that is still less than halfway around Earth, whose circumference is just over 40,000 km.
Why You Weigh Less on the Moon
Size differences also explain one of the Moon's most famous features: its weak gravity. Surface gravity on the Moon is 1.62 m/s², compared with Earth's 9.81 m/s² — almost exactly one-sixth. A person weighing 80 kg (176 lbs) on Earth would tip the scales at only about 13.3 kg (29 lbs) of equivalent weight on the Moon, even though their mass is unchanged.
This is why Apollo astronauts bounded and hopped rather than walked; ordinary strides launched them off the ground. The same feeble gravity is why the Moon has essentially no atmosphere — its pull is too weak to hold gas molecules over billions of years, leaving a vacuum where temperatures swing from about 127°C in direct sunlight to around -173°C in shadow.
How the Moon Ranks Among Solar System Moons
From Earth the Moon looks commanding, but among the solar system's natural satellites it ranks only fifth in size:
- Ganymede (Jupiter) — 5,268 km, larger than the planet Mercury
- Titan (Saturn) — 5,149 km, wrapped in a thick atmosphere
- Callisto (Jupiter) — 4,821 km
- Io (Jupiter) — 3,643 km
- The Moon (Earth) — 3,474 km
What truly sets our Moon apart is its size relative to its host planet. At 27% of Earth's diameter, it is by far the largest moon compared to its parent. Ganymede, the biggest moon overall, is only about 3.7% of Jupiter's width. This unusual ratio is why some astronomers describe the Earth-Moon pair as a near "double planet."
Distance and Scale Model
Size only tells half the story; the gap between the two worlds is vast. The Moon orbits at an average distance of 384,400 km (238,855 mi). Light crosses that gap in about 1.28 seconds, and the Apollo crews needed roughly three days to make the trip. Remarkably, the gap is wide enough that all seven other planets in the solar system could be lined up edge to edge between Earth and the Moon.
A simple scale model captures both size and distance at once: if Earth were a basketball, the Moon would be a tennis ball placed about 7 meters (23 feet) away. The Moon is also slowly retreating, drifting outward by about 3.8 cm each year. If you enjoy testing how well you can picture the world's dimensions, you can practice your sense of scale and place with our geography games.
Frequently Asked Questions
How many Moons could fit inside Earth?
About 49. Because volume scales with the cube of diameter, the Moon's 27% width translates to only roughly 2% of Earth's volume, so you would need close to 50 Moons to fill our planet.
Is the Moon bigger than any country?
Yes, in surface area. The Moon's 37.9 million km² exceeds the size of any single nation and is even slightly larger than the entire African continent. Russia, the largest country, would cover under half the lunar surface.
Why does the Moon look so large in the sky?
Its apparent size comes from being our nearest neighbor at 384,400 km, far closer than any other body. Its actual diameter, 3,474 km, is only about a quarter of Earth's — it simply appears prominent because it is close.
How much would I weigh on the Moon?
About one-sixth of your Earth weight, because lunar surface gravity (1.62 m/s²) is roughly a sixth of Earth's. Someone who weighs 80 kg on Earth would weigh the equivalent of around 13 kg on the Moon.
