How many days does the Moon take to orbit Earth (sidereal period)?

The Moon takes about 27.3 days to orbit Earth relative to the distant stars; this is called its sidereal orbital period. During that time, the Moon travels once around Earth while following a slightly elliptical path.

This figure is different from the roughly 29.5-day cycle between identical lunar phases, known as the synodic month. The difference exists because Earth is also moving around the Sun. After one sidereal orbit, the Moon must travel a little farther to line up with the Sun and reproduce the same phase.

The Moon’s orbital period is connected to its rotation period. It also rotates once in about 27.3 days, creating synchronous rotation. As a result, nearly the same hemisphere always faces Earth, although libration lets observers see slightly more than half of the lunar surface over time.

A common mistake is to answer 29.5 days when the question specifically says sidereal period. That number describes the phase cycle, while 27.3 days describes the Moon’s orbit measured against the stars.