Jupiter, the giant.
A storm bigger than Earth, a day shorter than a school day and a family of moons like a solar system in miniature. Every fact checked against NASA, JPL and ESA, plus a storm you can watch shrink, a moon-catching game and an eraser called Useless, who has brought an umbrella.
Watch a storm bigger than Earth shrink
NASA has measurements of the Great Red Spot going back to the 1800s. Pick a year and we’ll line Earths up across it, to scale.
Late 1800s: 25,500 miles across
Our drawing. The storm’s width and the Earths are to the same scale; the oval’s height is just for show, as these measurements are of the long axis only.
The measurements and where they come from
| Year | Long axis | Source |
|---|---|---|
| Late 1800s | 25,500 miles | NASA Science: Jupiter’s Great Red Spot is shrinking (2014) |
| 1979 | 14,500 miles | NASA Science: Jupiter’s Great Red Spot is shrinking (2014) |
| 1995 | 13,020 miles | NASA Science: Jupiter’s Great Red Spot is shrinking (2014) |
| 2009 | 11,130 miles | NASA Science: Jupiter’s Great Red Spot is shrinking (2014) |
| 2014 | 10,250 miles | NASA Science: Jupiter’s Great Red Spot is shrinking (2014) |
NASA gives these in miles. Kilometres, “Earths across” and the driving time are our own sums: 1 mile = 1.609344 km, and Earth is 12,756 km wide NASA NSSDC: Jupiter fact sheet. Astronomers have watched the Great Red Spot shrink since the 1930s, and from 2012 it shrank faster, turning from an oval towards a circle. NASA Science: Jupiter’s Great Red Spot is shrinking (2014) · checked 27 Oct 2026 Hubble watched it for 90 days in 2023–24 and saw it jiggle in size and shape, like a bowl of jelly. The cause is unknown. NASA Science: Hubble watches the Great Red Spot behave like a stress ball (2024) Juno’s gravity data suggest the Great Red Spot reaches about 500 km below the cloud tops. NASA Science: Jupiter facts
The short version
Jupiter is the fifth planet from the Sun, and the largest in the solar system by far. NASA Science: Jupiter Jupiter is more than twice as massive as all the other planets put together. NASA Science: Jupiter
If Earth were the size of a grape, Jupiter would be about as big as a basketball. NASA Science: Jupiter facts If Jupiter were a hollow shell, 1,000 Earths could fit inside. NASA Science: Jupiter
Like the Sun, Jupiter is made mostly of hydrogen and helium. NASA Science: Jupiter facts Jupiter has the same ingredients as a star, but it never grew massive enough to ignite. NASA Science: Jupiter facts
Jupiter has no true surface. It is mostly swirling gases and liquids, so a spacecraft would have nowhere to land. NASA Science: Jupiter facts With four large moons and many small ones, Jupiter is like a miniature solar system. NASA Science: Jupiter moons
How old, and how heavy, would you be on Jupiter?
A Jupiter year lasts 4,332.589 Earth days and a Jupiter day just 9.9259 hours, so the numbers get strange fast. Nothing you type leaves your browser.
Put in a birthday to find out
- Your age in Jupiter years
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- Your next Jupiter birthday
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- Jupiter days you’ve lived
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- Your weight at Jupiter’s cloud tops
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How it works: these are our own sums, using NASA’s Jupiter fact sheet. A Jupiter year is 4,332.589 Earth days NASA NSSDC: Jupiter fact sheet; a Jupiter day is 9.9259 hours NASA NSSDC: Jupiter fact sheet. Weight × 2.640, the gravity at Jupiter’s 1-bar cloud level compared with Earth’s NASA NSSDC: Jupiter fact sheet. You couldn’t actually stand there: jupiter has no true surface. It is mostly swirling gases and liquids, so a spacecraft would have nowhere to land. NASA Science: Jupiter facts
Explore Jupiter
JupiterSize, gravity, a 9.9-hour day and an ocean of hydrogen.
StormsThe Great Red Spot, polar cyclones, auroras and faint rings.
MoonsIo, Europa, Ganymede, Callisto and the rest.
MissionsFrom Pioneer 10 in 1973 to Juno, Europa Clipper and Juice.
Myths vs factsA failed star? Somewhere to land? Gently corrected.
The big facts pageEvery fact on the site, each one checked against its source.
Tile images are credited on their pages and on the credits page.
Things to play
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Jupiter printables
Fact-checked PDFs in A4 and US Letter, sold as instant downloads from the ReallyByte store.
Jupiter Storm Explorer Pack
Measure the shrinking Great Red Spot against Earths, graph it, map the belts and zones and design your own storm, with answer keys
Jupiter vs Earth Worksheets
Size, mass, days, years and gravity compared, with Jupiter-maths, a cutaway to label and answer keys
Jupiter Moons & Missions Cards
Twelve double-sided cards, from Io and Europa to Pioneer 10, Galileo, Juno and Juice, plus a timeline game
Jupiter Activity & Colouring Pack
Colouring scenes, a Juno maze, word search and puzzles for ages 4 to 9
Jupiter Facts Poster Set
Six fact-checked posters, from the 9.9-hour day to the four Galilean moons
Jupiter Quiz & Word Puzzles Pack
A crossword, code breaker, fill-the-gap facts, number match, myth busters and a 16-question quiz, with answer keys
Best valueThe Complete Jupiter Printables Bundle
All six packs plus a guide, A4 and US Letter, in one download.