How Many Grains of Sand are on Earth’s Beaches?

Learn how to estimate the number of grains of sand on all of Earth’s beaches. Here's Math Dude's trick to quickly estimate tough-to-calculate numbers.

Jason Marshall, PhD,
January 29, 2016
Episode #114

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Step 4: Calculate the Number of Sand Grains

Earth’s beaches contain roughly 5,000 billion billion—aka, 5 sextillion—grains of sand.

We’ve now estimated that there are about 8,000,000,000 = 8x10^9 grains of sand per cubic meter of beach, and that the Earth contains roughly 700,000,000,000 = 7x10^11 cubic meters of beach. Which means that we can find the number of sand grains on Earth’s beaches by multiplying these two numbers together. When we do that, we get 8x10^9 x 7x10^11 = 5.6x10^21. So Earth’s beaches contain roughly 5,000 billion billion—aka, 5 sextillion—grains of sand. Which, needless to say, is a HUGE number!

So that’s the answer we were looking for…and that’s how math can be used to make estimates that help you make sense of the world. If you’re feeling like a lot of this was just guessing, you’re right! But it wasn’t just wild random guessing—it was smart educated guessing based upon what we know about math and the world. And that’s precisely what making estimates is all about!

Wrap Up

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Until next time, this is Jason Marshall with The Math Dude’s Quick and Dirty Tips to Make Math Easier. Thanks for reading, math fans!

Beach image from Shutterstock


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