Neptune vs Earth
Neptune (49,528 km) is 3.89× the size of Earth (12,742 km).
3 Earths stacked on end would reach the height of Neptune. The gap between them is 36,786 km (120,688,976 ft).
The comparison in numbers
| Thing | Size | In feet | Measured as |
|---|---|---|---|
| Neptune | 49,528 km | 162,493,438 ft | diameter |
| Earth | 12,742 km | 41,804,462 ft | diameter |
What the scale shows
Neptune (49,528 km) is 3.89× the size of Earth (12,742 km). The gap between them is 36,786 km (120,688,976 ft). Both are planets & moons, so the figures describe the same kind of thing.
Draw both on one baseline and the smaller one fills 26% of the frame while the larger one runs to the top. The two are close enough that the difference is easy to see side by side.
Read the rest — 8 more sections
What each figure means
The figure for Neptune is its diameter (equatorial diameter). The figure for Earth is its diameter (mean diameter).
Crossing them
At a jet's 900 km/h, Neptune's 49,528 km would take 2.3 days and Earth's 12,742 km would take 14.2 hours.
In people: Neptune is 29,134,118 adults of 1.7 m tall, Earth is 7,495,294.1. By size Neptune is 5th of the 16 planets & moons on this site and Earth is 6th, so 1 place separates them in the ranking.
How to read these two figures
Before trusting any comparison, check what each number measures. Neptune is given as a diameter, equatorial diameter. Earth is given as a diameter, mean diameter. Both are diameter figures, so putting them on one baseline is a like-for-like comparison, although the exact individual or convention still matters.
Worlds are listed by diameter. Gas giants are not round, so equatorial diameter is used for them and mean diameter for the rest. All figures are rounded from published mission data.
Where the pair sits among all the sizes here
Across all 86 things on this site, Neptune is number 5 from the top and Earth is number 6. No other item falls between them, so in this collection they are direct neighbours.
Because the collection spans 13 mm up to 1,392,700 km, a ratio of 107,130,769,231× from smallest to largest, the position of a pair says a lot: both sit in the upper third of the list.
What the length ratio hides
A length ratio of 3.89× is easy to picture, but area and volume grow faster than length. If two objects had exactly the same shape, Neptune would have about 15.1× the surface or footprint of Earth, and about 58.7× the volume. These two are not the same shape, so treat the figures as an upper bound for an imaginary scaled copy, not as a measurement of either one.
The drawing above shows length only. Earth is drawn 26% as tall as Neptune, but the equivalent share of footprint would be only 6.6%, which is why the smaller one looks even slighter than the numbers alone suggest.
Time to cross each one
Light travels at 299,792,458 m/s, so it crosses Neptune (49,528 km) in 165 milliseconds and Earth (12,742 km) in 43 milliseconds. A jet at 900 km/h would take 2.3 days for the larger and 14.2 hours for the smaller.
These times assume a straight line and constant speed, which no real crossing has, but they turn a number in metres into something the body understands. At any fixed speed the travel times keep the same 3.89× ratio as the sizes.
The same figures in other units
Neptune measures 49,528 km, which is 162,493,438 ft or 30,775.3 miles. Earth measures 12,742 km, which is 41,804,462 ft or 7,917.51 miles.
The difference between them is 36,786 km (120,688,976 ft). In kilometres the smaller one is 12,742 against 49,528, so the 3.89× ratio holds in every unit; only the numbers on the ruler change.
Questions people ask about this pair
Which is bigger, Neptune or Earth?
Neptune is bigger. At 49,528 km it is 3.89× the size of Earth, which is 12,742 km.
How many times does Earth fit along Neptune?
3 whole times, with 11,302 km left over, using 12,742 km for each.
Are the two figures measured the same way?
Yes in kind: both are diameter figures. Neptune is equatorial diameter; Earth is mean diameter.
How does the gap look in people?
Taking an adult of 1.7 m, Neptune is about 29,134,118 people tall and Earth is about 7,495,294.1. The gap of 36,786 km is 21,638,824 people.
Where do the numbers come from?
Each item has its own page that names the measurement and links to the Wikipedia article it was taken from. Some figures are rounded, and animals vary from one individual to the next, so treat them as representative values rather than records for every case.
How the sizes are taken. Each figure says what it measures — height, length, diameter or elevation — and for which individual or convention. Everything is drawn standing upright on one baseline so a single scale holds, including things that are long rather than tall. Values come from the linked Wikipedia article for each item.