How long does it take Mercury to rotate on its axis?

Mercury takes about 58.7 Earth days to rotate once on its axis.

That figure is Mercury’s sidereal rotation period—the time needed to turn once relative to distant stars. Mercury rotates unusually slowly compared with Earth, which spins once in about 24 hours. Yet Mercury’s year is short: it completes one orbit around the Sun in only about 88 Earth days.

Mercury’s rotation and orbit are locked in a 3:2 spin-orbit resonance. It rotates three times for every two trips around the Sun. Because of this relationship and Mercury’s eccentric orbit, a solar day on the planet—from one sunrise to the next—lasts about 176 Earth days, much longer than its rotation period.

The 58.7-day answer is sometimes confused with Mercury’s 176-day solar day or its 88-day orbital period. All three numbers describe different cycles. Spacecraft observations, including measurements from Mariner 10 and MESSENGER, helped establish Mercury’s rotation behavior and its unusual resonance.