How big is Mercury compared to Earth?
38%of Earth’s width
Mercury is 38% of Earth’s width — 4,879 km across against Earth’s 12,742 km. By volume, Earth could hold about 18 of them. It has about 6% of Earth’s mass, and its surface gravity is 0.38× Earth’s.
▶ See Mercury next to Earth in 3D
Side by side
Width vs Earth
38% of Earth’s
Volume vs Earth
6% of Earth’s
Mass vs Earth
about 6% of Earth’s mass
Surface gravity
0.38× Earth (3.7 m/s²)
You’d weigh
26 kg (if 70 kg here)
Diameter
4,879 km
Mercury is small enough that roughly 18 of them would fit inside Earth.
What that actually feels like
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.
Ratios on a page are easy to nod along to and impossible to picture. In the interactive view, switch to True scale to see Mercury and Earth at their honest relative sizes.
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 Found something out of date?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.