How Big Is the Moon Compared to Earth

The moon has fascinated humans for millions of years, and the wonder and fascination are still as strong today. There are many unanswered questions about the moon, and new missions to the moon aim to answer some of them. Today we aim to answer the question of how big is the moon compared to earth. We then move into follow-up questions that the answer may leave you wondering.

The moon is 27 percent the size of the earth (one-fourth). No other planet and its moons have such a sheer difference in size than the 1:4 ratio. Earth’s moon is the fifth largest moon within our solar system.

Moon Compared to Earth

Okay, so we now know that the moon is 27 percent smaller than the earth, but this leads us to ask more questions. A moon is a fascinating object in our night sky, and many questions lead from an answered question.

What is the size of the moon?

Okay, so we know the earth’s size to the moon, but what is the moon’s size? The answer is not as simple as you may think. Just like the earth, the moon is not as perfectly round as we may think. The moon is a little squashed in shape; this makes measuring a bit more complicated.

There are two points that measurements of the moon are taken. These are pole to pole and the equator, with the latter being bigger than the former.

The moon’s pole to pole diameter size is 3,476km
The moon’s diameter from the equator is 3,472km

The difference is not all that big, but there is a difference. So, around 4km’s difference from the pole to pole and the equator measurement.

If you want the radius of the moon, you half the above sizes giving us.

The moon’s pole to pole radius size is 1,738km
The moon’s radius from the equator is 1,736km

It is worth pointing out that the moon’s equatorial circumference is 10,917 km.

What is the size of the earth?

As we touched on, just above the earth is not entirely round. The world has a bulge in its shape, and this gives us two measurements.

The earth’s polar radius is 6,356 km.
Measurements from the equator the earth is 6,378 kilometers radius

What this gives us a size difference of 22 km between the two measurements.

We can now work out the diameter of the earth with the above information easily.

The earth’s polar diameter is 12,712 km.

Measurements from the equator the earth is 12,756 kilometers in diameter

How big is the moon compared to the United States?

how big is the moon compared to united states

The most significant distance between two points in the united states is between Point Arena, California, and West Quoddy Head in Maine. The distance between the two is 4,656 km. A distance that doesn’t include Alaska or Hawaii, including them, would put the distance up by 3,340 km to a total of 7,996 km.

Making a comparison of the size between the moon and the USA is not as straightforward. As the moon is not 2D, it is 3D.

Above that, we found out that the moon’s equatorial circumference is 10,917 km, and the USA is 7,996 km.

So, including Alaska and Hawaii, the USA is around 73.2% of the moon’s circumference. If you don’t include Alaska and Hawaii, it’s approximately 42.6% of the moon’s circumference.

The United States of America wouldn’t fully wrap around the moon. Our image below gives you a good idea of how much of the moon the USA would cover the moon.

Is Australia bigger than the moon?

how big is the moon compared to Australia

A follow-up question may be is Australia bigger than the moon as we know Australia is a big country.

The distance between Australia’s east and west coast is 4,030 km as the crow flies. If you go from north to south, it’s a little smaller at 3,685 km.

Australia would only cover around 36.9% of the surface of the moon. Like the USA, it is harder to compare the two as the moon is 3D, and Australia is 2D.

Is Australia or the USA bigger?

So we have seen how much both the USA and Australia would cover the surface of the moon. It should give you an idea of whos bigger but let’s break it down.

Australia is 7.69 million square kilometers, and the USA is 9.16 million square kilometers.

With this, the USA is 1,470,00 million square kilometers larger than Australia or 19.11% larger.

How long would it take to walk around the moon?

If we use the moon’s equatorial circumference of 10,917 km, we will work out the calculation from this number.

If we say that, we could walk 60km per day for our workings below to make it simple.

It would take someone walking 60km per day just shy of 182 at 181.95 days. You would have to be super fit as the moon’s terrain is not even and not forgetting any injuries.


So, we found out that the moon is smaller than our earth and that the US and Australia would fill a large portion of the moon’s surface.

So next time, you pull out the best telescope to see the moon to start a night of moongazing. You should have a lot more knowledge of our closest neighbor, the moon.

There are many discoveries of the moon happening, and there is set to be more with space missions to the moon happening soon. If you are looking for a new assignment with your telescope, the lunar 100 is a tremendous challenge.