Mars vs Ganymede
Mars (6,779 km) is 1.29× the size of Ganymede (5,268 km).
Ganymede is 78% of the height of Mars. The gap between them is 1,511 km (4,956,693 ft).
The comparison in numbers
| Thing | Size | In feet | Measured as |
|---|---|---|---|
| Mars | 6,779 km | 22,240,814 ft | diameter |
| Ganymede | 5,268 km | 17,284,121 ft | diameter |
What the scale shows
Mars (6,779 km) is 1.29× the size of Ganymede (5,268 km). The gap between them is 1,511 km (4,956,693 ft). Both are planets & moons, so the figures describe the same kind of thing.
Draw both on one baseline and the smaller one fills 78% 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 Mars is its diameter (mean diameter). The figure for Ganymede is its diameter (mean diameter).
Crossing them
At a jet's 900 km/h, Mars's 6,779 km would take 7.5 hours and Ganymede's 5,268 km would take 5.9 hours.
In people: Mars is 3,987,647 adults of 1.7 m tall, Ganymede is 3,098,941.2. By size Mars is 8th of the 16 planets & moons on this site and Ganymede is 9th, so 1 place separates them in the ranking.
How to read these two figures
Before trusting any comparison, check what each number measures. Mars is given as a diameter, mean diameter. Ganymede 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, Mars is number 8 from the top and Ganymede is number 9. 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 1.29× is easy to picture, but area and volume grow faster than length. If two objects had exactly the same shape, Mars would have about 1.66× the surface or footprint of Ganymede, and about 2.13× 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. Ganymede is drawn 78% as tall as Mars, but the equivalent share of footprint would be only 60.4%, 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 Mars (6,779 km) in 23 milliseconds and Ganymede (5,268 km) in 18 milliseconds. A jet at 900 km/h would take 7.5 hours for the larger and 5.9 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 1.29× ratio as the sizes.
The same figures in other units
Mars measures 6,779 km, which is 22,240,814 ft or 4,212.3 miles. Ganymede measures 5,268 km, which is 17,284,121 ft or 3,273.51 miles.
The difference between them is 1,511 km (4,956,693 ft). In kilometres the smaller one is 5,268.2 against 6,779, so the 1.29× ratio holds in every unit; only the numbers on the ruler change.
Questions people ask about this pair
Which is bigger, Mars or Ganymede?
Mars is bigger. At 6,779 km it is 1.29× the size of Ganymede, which is 5,268 km.
How many times does Ganymede fit along Mars?
Less than twice: Ganymede is 78% of the size of Mars, so one fits with 1,511 km to spare.
Are the two figures measured the same way?
Yes in kind: both are diameter figures. Mars is mean diameter; Ganymede is mean diameter.
How does the gap look in people?
Taking an adult of 1.7 m, Mars is about 3,987,647 people tall and Ganymede is about 3,098,941.2. The gap of 1,511 km is 888,706 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.