Mars
A whole world of what if.
How big is Mars? Mars is 6,792 km (4,220 miles) across at its equator — 0.53 times Earth’s width (about 53%) — and about 6.6 Mars-sized worlds would fit inside Earth. Gravity at the surface is 3.7 m/s², 0.38 times Earth’s.
Mars is a cold desert with rusty soil, enormous volcanoes, and evidence that liquid water once flowed across its surface. Its thin atmosphere offers little insulation.
Image: NASA / JPL-Caltech. Processed mission imagery; apparent color varies with filters and processing.
Mars quick facts
| Planet type | Terrestrial planet |
|---|---|
| Equatorial diameter | 6,792 km (4,220 mi) |
| Mean radius | 3,389.5 km (2,106 mi) |
| Size compared with Earth | 0.53× as wide · 0.151× the volume |
| Equatorial circumference | 21,338 km (13,259 mi) |
| Surface area | 1.44 × 10⁸ km² |
| Volume | 1.63 × 10¹¹ km³ |
| Mass | 6.42 × 10²³ kg (0.108 Earth masses) |
| Mean density | 3,934 kg/m³ (3.93 g/cm³) |
| Surface gravity | 3.7 m/s² (0.38× Earth) |
| Escape velocity | 5 km/s |
| Length of day (solar) | 24.7 hours |
| Rotation period (sidereal) | 24.6 hours |
| Orbital period (year) | 687 Earth days (1.88 Earth years) |
| Mean distance from the Sun | 228 million km (141.7 million mi) · 1.52 AU |
| Closest and farthest from the Sun | 206.7 – 249.3 million km |
| Distance from Earth | 54.6 – 401.4 million km |
| Sunlight travel time | 12.7 minutes |
| Mean orbital speed | 24.1 km/s |
| Axial tilt | 25.2° |
| Mean temperature | -65 °C |
| Known moons | 2 |
| Ring system | No |
Reference: NASA Planetary Fact Sheet. Rounded values; diameters are equatorial, area and volume use the mean radius. Moon counts include discoveries announced through 2025 (such as Uranus’s S/2025 U1) and keep growing as new moons are confirmed.
How big is Mars compared to Earth?
Mars’s equatorial diameter of 6,792 km makes it 0.53 times Earth’s width (about 53%). By volume, about 6.6 Mars-sized worlds would fit inside Earth. Its mass is 0.108 times Earth’s, so its average density is similar: 3,934 kg/m³ (3.93 g/cm³).
Earth’s equatorial diameter is 12,756 km (7,926 miles). See every planet to scale ↗
What is the gravity on Mars?
Gravity on Mars is about 3.7 m/s² at the surface: 0.38 times Earth’s 9.8 m/s². Someone who weighs 100 lb on Earth would weigh about 38 lb on Mars. To escape its pull, a rocket needs 5 km/s.
Calculate your weight on Mars ↗How far is Mars from the Sun and Earth?
Mars orbits an average 228 million km (141.7 million miles, 1.52 AU) from the Sun, ranging from 206.7 to 249.3 million km. Sunlight takes 12.7 minutes to get there. Its distance from Earth varies from about 54.6 to 401.4 million km.
Time sunlight’s journey ↗How long is a day and a year on Mars?
A solar day on Mars lasts 24.7 hours, and one spin relative to the stars takes 24.6 hours. A year — one trip around the Sun at 24.1 km/s — lasts 687 Earth days (1.88 Earth years). Its axis is tilted 25.2°.
Watch the orbit ↗Is Mars a rocky planet or a gas giant?
No. Mars is a terrestrial, or rocky, planet with a solid surface of rock and metal — one of the four inner planets with Mercury, Venus, Earth and Mars. The gas giants are Jupiter and Saturn.
Meet all eight planets ↗Mars questions, answered
How big is Mars compared to Earth?
Mars is 6,792 km (4,220 miles) wide at its equator, 0.53 times Earth’s width (about 53%). By volume, about 6.6 Mars-sized worlds would fit inside Earth, and its mass is 0.108 times Earth’s.
What is the gravity on Mars?
Gravity on Mars is about 3.7 m/s² at the surface, or 0.38 times Earth’s. Someone who weighs 100 lb on Earth would weigh about 38 lb there; escape velocity is 5 km/s.
What is the mass of Mars?
Mars has a mass of about 6.42 × 10²³ kg, or 0.108 Earth masses. Its mean density is 3,934 kg/m³ (3.93 g/cm³).
How far is Mars from Earth?
The distance changes as both planets orbit the Sun. Mars comes within about 54.6 million km of Earth and can be as far as 401.4 million km away. It orbits 1.52 AU from the Sun on average.
How long is a year on Mars?
One orbit takes about 687 Earth days (1.88 Earth years). A solar day on Mars lasts 24.7 hours.
Is Mars a rocky planet or a gas giant?
No. Mars is a terrestrial, or rocky, planet with a solid surface of rock and metal — one of the four inner planets with Mercury, Venus, Earth and Mars. The gas giants are Jupiter and Saturn.
What is the density of Mars?
Mars’s mean density is 3,934 kg/m³ (3.93 g/cm³). Earth’s is 5,514 kg/m³.