SpaceWhat the picture shows
Each circle is drawn in proportion to the planet's real diameter. Jupiter, 142,984 km across, fills the picture. Earth, at 12,756 km, is a small dot beside it, and Mercury is barely visible. It would take 11.2 Earths in a row to span Jupiter, and 9.4 to span Saturn.
Diameter and mass, compared with Earth
| World | Diameter (km) | Diameter (Earth = 1) | Mass (Earth = 1) |
|---|---|---|---|
| Jupiter | 142,984 | 11.21 | 317.9 |
| Saturn | 120,536 | 9.45 | 95.1 |
| Uranus | 51,118 | 4.01 | 14.5 |
| Neptune | 49,528 | 3.88 | 17.1 |
| Earth | 12,756 | 1 | 1 |
| Venus | 12,104 | 0.95 | 0.816 |
| Mars | 6,792 | 0.53 | 0.108 |
| Mercury | 4,879 | 0.38 | 0.055 |
| Moon | 3,475 | 0.27 | 0.012 |
| Pluto | 2,376 | 0.19 | 0.002 |
Figures: NASA NSSDCA Planetary Fact Sheet, last updated by NASA on 18 March 2025, read on 12 November 2026.
Width is not the whole story
Saturn is 9.4 times as wide as Earth but only 95 times as massive, because it is made mostly of light gases. Uranus is a little wider than Neptune (51,118 km against 49,528 km), yet Neptune is the heavier of the two: 102 against 86.8, in units of 10²⁴ kg.
Venus is often called Earth's twin for its size: it is 95% of Earth's width. The Moon is 27% of Earth's width, which is unusually large for a moon compared with its planet. Pluto, at 2,376 km, is smaller than our Moon.
The Sun on the same scale
The Sun does not fit in the picture at all. It holds 99.8% of the mass of the solar system and is about 332,900 times as massive as Earth.
Why the picture leaves out the gaps
If the distances were drawn to the same scale as the sizes, the picture would be useless. If Jupiter were drawn 4 cm wide, Neptune would have to be placed more than a kilometre away. Space is mostly empty, and the planets are specks in it. That is why books show sizes and distances in separate pictures.
Make a model
If Earth were a marble 1 cm across, Jupiter would be a ball about 11.2 cm across and Saturn about 9.4 cm. Mercury would be a bead under 4 mm, and the Moon a grain about 2.7 mm wide.