How Much Does the Earth Weigh?

The Earth has a mass of about 5.97 x 10^24 kilograms, which works out to roughly 13 septillion pounds. We worked it out using the gravitational constant, a number first pinned down in the 1798 Cavendish experiment. Technically the Earth does not weigh anything on its own, since weight needs another object's gravity to pull against, so what we really mean is its mass.

Mass versus weight

Weight is how hard gravity pulls on you, which means you need something else doing the pulling. You weigh less on the Moon and more on Jupiter, but your mass never changes no matter where you go.

The Earth has nothing standard pulling on it the way a planet pulls on you, so it has mass, not weight. When people say Earth "weighs" 5.97 x 10^24 kilograms, they really mean its mass.

It is a small distinction that trips up almost everyone, including science textbooks. But once it clicks, the question "how much does the Earth weigh" becomes "how much matter is in it," which is a question that actually has a clean, fixed answer no matter where in the universe you ask it.

How we figured it out

You cannot put a planet on a scale, so scientists used gravity itself as the measuring tool. In the 1798 Cavendish experiment, Henry Cavendish measured the tiny gravitational tug between lead weights suspended in a lab.

That experiment nailed down the gravitational constant, the number that links mass and gravitational force. Once you know that constant and how Earth's gravity behaves at the surface, the planet's mass falls right out of the equations.

It is a genuinely beautiful piece of science: a few lead balls and a delicate balance let one person weigh the entire planet without leaving the room.

The setup was almost absurdly sensitive. The gravitational tug between the lab weights was so faint that Cavendish had to shield the apparatus from air currents and watch it through a telescope to avoid disturbing the measurement with his own body heat.

Putting the number in perspective

Roughly 13 septillion pounds is a number the human brain cannot really hold. That is a 13 followed by 24 zeros, a quantity with no everyday comparison.

It is so large that the planet's mass barely flinches even as space constantly throws material at it.

• Mass: about 5.97 x 10^24 kilograms
• In pounds: roughly 13 septillion
• Method: derived from the gravitational constant
• Key experiment: Cavendish, 1798

Earth is slowly getting heavier

The planet gains about 40,000 tons of space dust and micrometeorites every year as it sweeps through debris scattered along its orbit.

That sounds like a lot, but against 5.97 x 10^24 kilograms it is a rounding error so small it would never show up. Earth's mass is effectively constant on any human timescale, and will be for as long as anyone is around to measure it.

You cannot weigh a planet, but you can outsmart one with two lead balls and clever math.

Where the mass actually is

Most of Earth's mass is locked in the parts you never see. The dense iron-and-nickel core and the thick rocky mantle account for the overwhelming majority of it.

The crust we live on, oceans and continents and all, is a thin skin by comparison. The water in every ocean combined is a tiny fraction of the whole, and the atmosphere barely registers at all.

So when you stand outside, almost everything pulling you down is rock and metal miles beneath your feet. The planet you can see is just the wrapping on a very, very heavy package. It is a strange thing to sit with: the dramatic mountains and deep oceans that define our world are barely a footnote in the total, while the real bulk is hidden somewhere you will never visit.

Try It Yourself

Want to mess around with the ideas above? On whatifs.fun, Solar System, Gravity Playground and Size of Space all let you do exactly that — free, in your browser, no download.

Keep reading: how fast the Earth spins and how old the Earth is. Both go deeper on the same rabbit hole.