How much of the world is the United States?

"Is the United States about a tenth of the world?" Believe or not, my almost-six year old asked this last night. Her big sisters have been doing a lot of fractions, and we talk about sizes of things.

I wasn't sure.

First I figured I'd need to know the size of the world, and looked up a slightly useful term 'earth land mass' (I did explain to her about the oceans taking up about 2/3 of the earth's surface). That got me Wikipedia Earth but in a quick scan I didn't see the surface area, and let myself have a bit of fun and calculate it as 4*pi*r2, or 4 * 3.14 * (12,742 km/2)2. This has a bit of rounding error and I came up with 498 million square kilometers, which is a bit less than the answer I would have seen right in the google results if I'd just scanned down a bit: 510.072 million sq km land: 148.94 million sq km water: 361.132 million sq km.

Then I figured to look up 'United States land area' and also 'Russia land area' (I'd told my daughter I didn't think the US was 10% of the land, but Russia might be) and found the whole percentage list precalculated in order!

So the answer is, looking only at land area, the United States is about 6.5% of the total and Russia is about 11.5%. So my 6-year old had a pretty good handle on it!

(and the order between China and the US sparked a few discussions among the older kids, and we learned that there are significant territorial disputes between China and India - enough to make the difference between China 3rd largest or 4th largest country)

Now we might use the country order chart for back-of-car quizzes, I think I'll let the kids quiz me as its something they haven't really studied.