Mercury
4,879 kmacross
Mercury is 4,879 km across (2.6× narrower than Earth) and orbits the Sun at 0.39 AU — about 58,343,169 km. Sunlight takes 3.2 minutes to reach it. The smallest planet and the closest to the Sun — a scorched, airless, cratered world that looks a lot like our Moon.
▶ Visit Mercury in 3D
What kind of world is it?
Mercury is a world of brutal extremes. With almost no atmosphere to trap or move heat, the day side roasts at over 400 °C while the night side falls to −180 °C — the biggest temperature swing of any planet. Its huge iron core makes it the second-densest planet after Earth, and its cratered surface records four billion years of impacts almost untouched.
A solar day on Mercury (sunrise to sunrise) lasts two of its years. And it isn’t even the hottest planet.
Mercury by the numbers
Diameter
4,879 km
Distance from the Sun
0.39 AU
Sunlight travel time
3.2 minutes
Surface gravity
3.7 m/s²
Temperature
167 °C average
A day lasts
59 Earth days
A year lasts
88 Earth days
Known moons
0
Numbers only get you so far. The distances are the part nobody's brain handles — in the interactive view, switch to 1:1 scale and watch Mercury shrink to an honest speck on an enormous empty orbit.
Keep going
✓ Facts verified July 2026
Every figure on this page is a real, rounded value checked against primary sources. Found something out of date? See how we keep it accurate.