Moon Diameter Comparison (NASA Figures)
Compare 14 solar system moon diameters: Charon 1214, Io 3643, Europa 3122, Moon 3474, Titan 5150 and Ganymede 5260. Official NASA figures in km in one table.
Visual comparison
All values
Click any row to load it as Entry A.
| Name | Value | Context | Source |
|---|---|---|---|
| Ariel 1158 km. Smallest row here. | 1,158 kilometers | Uranus, brightest large moon | NASA Uranus moons facts: Ariel 1,157.8 km |
| Umbriel 1169 km. | 1,169 kilometers | Uranus, darkest large moon | NASA Uranus moons facts: Umbriel 1,169.4 km |
| Charon 1214 km. 754 miles across. | 1,214 kilometers | Pluto, half of Pluto | NASA Pluto moons: Charon 1,214 km |
| Iapetus 1472 km. Twice 736 radius. | 1,472 kilometers | Saturn, third largest | NASA Saturn moons: Iapetus radius 736 km |
| Oberon 1523 km. | 1,523 kilometers | Uranus, second largest | NASA Uranus moons facts: Oberon 1,522.8 km |
| Rhea 1528 km. Twice 764 radius. | 1,528 kilometers | Saturn, second largest | NASA Saturn moons: Rhea mean radius 764 km |
| Titania 1578 km. Uranus largest. | 1,578 kilometers | Uranus, largest | NASA Uranus moons facts: Titania 1,577.8 km |
| Triton 2700 km. 1680 miles. | 2,700 kilometers | Neptune, largest, retrograde | NASA Neptune moons: Triton 2,700 km |
| Europa 3122 km. 90 percent of our Moon. | 3,122 kilometers | Jupiter, fourth Galilean | NASA Jupiter moons: Europa 3,122 km |
| Moon 3474 km. Twice 1740 radius. | 3,474 kilometers | Earth, only natural satellite | NASA Moon facts: radius 1,740 km |
| Io 3643 km. Most volcanic world. | 3,643 kilometers | Jupiter, third Galilean | NASA Jupiter moons: Io 3,643 km |
| Callisto 4821 km. From 15144 circumference. | 4,821 kilometers | Jupiter, second largest | NASA Jupiter moons: Callisto circumference 15,144 km |
| Titan 5150 km. Twice 2575 radius. | 5,150 kilometers | Saturn, largest | NASA Saturn moons: Titan radius 2,575 km |
| Ganymede 5260 km. Priciest row here. | 5,260 kilometers | Jupiter, largest anywhere | NASA Jupiter moons facts: Ganymede 5,260 km |
About this converter
NASA mean diameters put moons on one ruler in km. Ariel opens at 1158. Umbriel reads 1169. Charon reads 1214 at half of Pluto. Iapetus reads 1472. Oberon reads 1523. Rhea reads 1528. Titania reads 1578 as Uranus largest. Triton reads 2700 with a retrograde orbit. Europa reads 3122 at 90 percent of our Moon. Our Moon reads 3474. Io reads 3643 as the most volcanic world. Callisto reads 4821 from its circumference. Titan reads 5150 from twice its 2575 radius. Ganymede tops the table at 5260 as the largest moon anywhere. One Ganymede spans more than 4.3 Charons. Bigger than Mercury, Ganymede and Titan both beat a planet.
How to use it
Pick two moons and a unit in the top row. The three boxes below stay linked. Change any box and the other two update. Try 1 Ganymede against Charons to see how many Pluto companions one giant spans.
Radius sourced rows double the NASA radius, like Titan at twice 2575 and the Moon at twice 1740, with the math noted per row. Callisto diameter derives from its 15144 km circumference and stays noted. Uranus values come from the NASA facts table via JPL dynamics. Pluto stays a dwarf planet in context while Charon keeps its moon row.
FAQ
What is the largest moon?
Ganymede at 5260 km around Jupiter. Titan follows at 5150 around Saturn and Callisto at 4821 around Jupiter.
How big is our Moon?
3474 km from twice the 1740 km NASA radius. Europa at 3122 is about 90 percent of it.
How big is Charon?
1214 km across, about half of Pluto. One Ganymede spans more than 4.3 Charons.
Are any moons bigger than Mercury?
Yes. Ganymede at 5260 and Titan at 5150 both beat Mercury, which the planet diameter page covers.
Sources
- NASA Jupiter moons facts pages (Ganymede 5,260 km, Callisto circumference, Io 3,643 km, Europa 3,122 km)
- NASA Saturn moons pages (Titan radius 2,575 km, Rhea radius 764 km, Iapetus radius 736 km)
- NASA Moon facts page (radius 1,740 km)
- NASA Neptune Triton page (2,700 km), Uranus moons facts table (Titania, Oberon, Umbriel, Ariel)
- NASA Pluto Charon page (1,214 km)
Last verified: 2026-10-01 · 14 entries
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