How big is Mars compared to Mercury?
1.4×wider than Mercury
Mars is 1.4× wider than Mercury — 6,779 km across against Mercury’s 4,879 km. By volume, about 3 Mercuries would fit inside Mars. Mars has 1.9× Mercury’s mass.
▶ See Mars and Mercury in 3D
Side by side
Diameter
Mars 6,779 km · Mercury 4,879 km
Width ratio
Mars is 1.4× wider
Volume
3 Mercuries fit inside Mars
Mass
Mars is 1.9× Mercury
Gravity (Mars · Mercury)
3.7 m/s² · 3.7 m/s²
Distance from Sun
1.52 AU · 0.39 AU
Mercury is only a little larger than our own Moon, and smaller across than Jupiter’s moon Ganymede.
What sets them apart
The two smallest planets. Mars is about 1.4 times wider than Mercury and nearly twice its mass. Both are small enough that the solar system’s largest moons, Ganymede and Titan, are actually wider than Mercury — though far less dense.
Ratios are easy to nod along to and impossible to picture. In the interactive view, switch to True scale to see Mars and Mercury 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 Found something out of date?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.