Is Mercury wider than the Moon in physical diameter?
Yes. Mercury, at 4,879 km, is wider than the Moon, at 3,475 km: about 1.4 times as wide.
The duel opens first in a practice round of ten; practice never changes your daily streak.
Why it surprises
Mercury is the smallest planet in the solar system, and the Moon looks large in our sky, so it is easy to suspect the Moon might be the bigger of the two. It is not. Mercury’s diameter is about 4,879 km and the Moon’s about 3,475 km, so Mercury is about 1.4 times as wide. “Smallest planet” is a title within a group of eight; it does not mean smaller than every moon. The Moon looks big only because it is so close to us, while Mercury, much further away, appears in the sky as a bright point near the Sun. Comparing physical width removes that effect. If the two were placed side by side, Mercury would be clearly the larger, though still well under half as wide as Earth.
Sources for this explanation
- European Space Agency: esa.int, checked 25 October 2026
- NASA Goddard Space Flight Center: nssdc.gsfc.nasa.gov, checked 25 October 2026
Where the numbers come from
Each value was checked against two independent sources, quoted on its page. Details: Mercury and The Moon.
Spotted a mistake? Tell us; a correction gets a new revision.