The Short Answer
The Earth has a mass of about 5.97 x 10^24 kilograms. Written out in full that’s roughly 6,000,000,000,000,000,000,000,000 kilograms, a 6 followed by 24 zeros, which scientists call six septillion. It’s a number so large it stops meaning much, but it’s the honest answer to how heavy our planet really is.
There’s a small but important twist hiding in this question, though. Strictly speaking, the Earth doesn’t “weigh” anything at all, at least not in the way you weigh yourself on a bathroom scale. What we’re really asking about is the Earth’s mass, and the difference between the two turns out to be the key to the whole story. So let’s unpack the number, sort out weight from mass, and look at the clever way we figured it out without ever putting the planet on a scale.
Weight or Mass? They’re Not the Same Thing
Here’s the distinction that trips everyone up. Weight is how hard gravity pulls on an object, while mass is how much actual stuff, how much matter, that object contains. On Earth the two feel interchangeable, but they come apart the moment gravity changes.
Take yourself to the Moon and you’d weigh only about a sixth of what you do here, because the Moon’s gravity is weaker. Yet you’d still be made of exactly the same amount of material, so your mass wouldn’t budge. That’s why asking what the Earth “weighs” is a bit of a trick question. Weight needs something to be pulling on you from outside, and there’s nothing standing outside the Earth weighing it. So scientists skip the confusion and talk about mass instead, which stays the same no matter where you are. If you’d like to feel that difference for yourself, our weight on other planets calculator shows how your own weight would swing from world to world.
So How Do You Weigh a Whole Planet?
This is the genuinely brilliant part. You obviously can’t lift the Earth onto a scale, so how did anyone ever measure its mass? The answer came from an experiment done more than two centuries ago.
In 1798 a reclusive English scientist named Henry Cavendish set up a delicate apparatus with lead spheres hanging from a thin fibre, designed to detect the faint gravitational tug between the masses. By measuring how strongly two ordinary objects pulled on each other, he pinned down the strength of gravity itself, a value known today as the gravitational constant. Once you know that number, along with the size of the Earth and the strength of gravity at its surface, a bit of maths hands you the planet’s mass. Cavendish had, in effect, weighed the world using nothing but some lead balls and extraordinary patience. Every estimate of Earth’s mass since then traces back to that basic idea.
Putting Six Septillion Into Perspective
A number like six septillion is impossible to picture, so it helps to compare it to things we already know. The trouble is that nothing in everyday life comes remotely close, which is really the whole point.
Where the comparison starts to work is with other worlds. Our Moon, for instance, has only about one eightieth of Earth’s mass. Go the other way and the scale runs away from us fast. The giant planet Jupiter weighs in at roughly 318 times the mass of Earth, as we explore in our guide to Jupiter’s size, distance, and orbit. And the Sun utterly dwarfs them all, packing about 333,000 Earths’ worth of mass into a single star, a figure we get into in what sort of star the Sun is. Against those, Earth is a fairly modest lump of rock and metal.
Is the Earth Getting Heavier or Lighter?
You might assume a planet’s mass is fixed forever, but it actually drifts by tiny amounts. Every year the Earth gains a bit of mass as thousands of tonnes of space dust and micrometeorites drift down through the atmosphere and settle onto the surface.
At the same time, it slowly loses mass too, as lightweight gases like hydrogen and helium leak away from the top of the atmosphere into space. When you tally it all up, the losses slightly outweigh the gains, so the Earth is very gradually shedding a little weight. But the amounts involved are utterly trivial next to six septillion kilograms, so for all practical purposes the planet’s mass is rock steady.
So there’s the full picture. The Earth’s mass is about 5.97 x 10^24 kilograms, we measured it by weighing gravity rather than the planet itself, and it’s neither truly gaining nor losing in any way that matters. Not bad for a question you can’t answer with an ordinary scale. For more about the world beneath our feet, NASA’s Earth page is a great place to keep exploring.
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