How Big is the Moon?

Earth’s moon is the brightest object in our night sky. But how big is the moon? The moon’s mean radius is 1,079.6 miles (1,737.5 kilometers) and the mean diameter is 2,159.2 miles (3,475 km), which is 27% of Earth’s diameter of 7,901 miles (12,715.43 km) at the poles. Compared to Earth, the moon is less than a third the width of our home planet, according to NASA. The moon’s equatorial circumference is 6,783.5 miles (10,917 km).

Our Moon, which lies an average distance of about 238,857 miles (384,403 km) from Earth, appears in our sky as nothing more than a glowing orb reflecting starlight from the Sun back to our little planet, making it difficult to to capture it is the actual size of our natural satellite, as it is only half a degree in our night sky and differs only slightly from how far away the moon is from earth at any point in time.

The moon’s mass is 7.35 x 1022 kg, about 1.2% of Earth’s mass. Put another way, Earth weighs 81 times more than the moon. The moon’s density is 3.34 grams per cubic centimeter (3.34 g/cm3). That is about 60% of Earth’s density.

To really capture the moon’s size, a Redditor created this incredible image of the moon’s far side, which the United States sits on. This is a good comparison as the distance across the US is about half the circumference of the moon. (Fun fact: if the Earth were hollow, 50 moons could fit in) Now, the greatest distance between any two points in the US is 2,892, which is from Point Arena in California and West Quoddy Head in Maine.

How big is the Moon compared to the Earth?

This one’s another easy approximation to remember: The Moon is about one-fourth (or a quarter) the size of Earth in width. Put another way, Earth is about four times wider than the Moon. That’s just about as wide as the United States or Europe.

The moon is a bit more than one-quarter (27 percent) the size of Earth, a much larger ratio (1:4) than any other planets and their moons. Earth’s moon is the fifth largest moon in the solar system.

What if the moon was twice as big?

If the moon were twice as big, solar eclipses would occur even more frequently. The path of totality would be significantly wider, perhaps over 3,600 km/2,000 mi – the expanse of the moon’s umbra. Totality would last much longer, perhaps more than an hour.

During totality, the sky would be much darker than before, and the annular eclipse would cease to exist. Tides would be significantly larger on Earth, but that assumes the moon has the same mass. If it didn’t, it would be very likely that it would collide with our Earth.

How many moons fit in the sun?

The sun is gigantic, and if it were hollow, it could be filled with around 64.3 million Earth’s moons. If you could fill it with Earth-sized planets, you would need about 1.3 million Earths.

The Sun has a radius of 696,340 km/432,685 mi and a diameter of 1.39 million km/864,000 mi. It is 330,000 times more massive than Earth.


  1. Wikipedia
  2. NASA
  3. Space