Jupiter’s diameter is about 11 times larger than Earth’s diameter.
The comparison uses diameter—the distance across a planet—not volume or mass. Jupiter’s equatorial diameter is roughly 142,984 kilometers, while Earth’s is about 12,742 kilometers. Dividing the two gives approximately 11.2, commonly rounded to 11.
That ratio does not mean Jupiter is only 11 times larger in every way. Because volume scales with the cube of diameter, roughly 1,300 Earths could fit inside Jupiter by volume, although Jupiter’s cloud layers and internal structure make the real packing comparison more complicated. Jupiter’s mass is about 318 Earth masses.
Jupiter is the Solar System’s largest planet and a gas giant made mostly of hydrogen and helium. Its rapid rotation causes a noticeable equatorial bulge, so its equatorial diameter is slightly greater than its polar diameter.