Mercury whips around the Sun in just 88 Earth days, while Neptune takes 165 Earth years — a single Neptunian year has spanned the entire history of modern astronomy.
Quick answer: 1. Mercury, 2. Venus, 3. Earth, 4. Mars, 5. Ceres, 6. Jupiter, 7. Saturn, 8. Uranus, 9. Neptune, 10. Pluto.
A planet's orbital period — the time it takes to complete one lap around the Sun — is determined primarily by its distance from the Sun, governed by Kepler's Third Law: the square of a planet's orbital period is proportional to the cube of its semi-major axis. The inner planets take just months, while the outer giants take decades or centuries. This list ranks the eight official planets of the Solar System plus the two largest dwarf planets (Pluto and Eris) by their orbital period, from shortest to longest. Eris, the most distant known dwarf planet, takes more than twice as long as Neptune to complete a single orbit.
The innermost planet completes an orbit in just 88 Earth days, traveling at an average speed of 47.4 km/s — the fastest orbital velocity of any planet in the Solar System. A Mercurian solar day (sunrise to sunrise) lasts 176 Earth days, meaning a full day is longer than the planet's year.
Venus takes 224.7 Earth days to orbit the Sun, but spins so slowly that its sidereal rotation period (243 Earth days) is longer than its year. It also rotates retrograde — the Sun rises in the west and sets in the east.
Our home planet defines the baseline: 365.25 days — the length of our year — is the reference against which all other planetary orbital periods are measured. The extra 0.25 days accumulate into a leap day every four years.
The Red Planet's 687-Earth-day orbit takes it nearly twice as long as Earth to circle the Sun, which is why Mars oppositions (when it appears brightest in our sky) occur only about every 26 months. A Martian year is 1.88 Earth years.
The largest object in the asteroid belt and the closest dwarf planet to the Sun, Ceres takes 4.6 Earth years to complete an orbit. It was the first asteroid ever discovered (1801) and was later reclassified as a dwarf planet in 2006.
The largest planet in the Solar System takes 11.86 Earth years to orbit the Sun. Despite its immense size, Jupiter rotates faster than any other planet — its day is just under 10 hours — which gives it a noticeably flattened shape at the poles.
The ringed planet takes 29.46 Earth years to complete one orbit. Its axial tilt of 26.7 degrees produces dramatic seasonal changes across its long year, with each season lasting more than seven Earth years.
The first planet discovered with a telescope (1781), Uranus takes 84.01 Earth years to orbit the Sun. It rotates on its side with an axial tilt of 97.8 degrees, meaning its poles experience 42 years of continuous sunlight followed by 42 years of darkness.
The outermost planet takes 164.8 Earth years to orbit the Sun. It was discovered in 1846 through mathematical prediction by Urbain Le Verrier, and has completed only one full orbit since its discovery (it returned to its discovery position in 2011).
The most famous dwarf planet takes 248 Earth years to complete one orbit. Its highly elliptical orbit takes it from 29.7 AU at perihelion to 49.3 AU at aphelion, meaning it occasionally crosses inside Neptune's orbit. Since its discovery in 1930, Pluto has completed less than 40% of one orbit.
| # | Name | type | meanDistanceFromSun | discovery | numberOfMoons |
|---|---|---|---|---|---|
| 1 | Mercury | Terrestrial | 57.9 million km | Ancient | 0 |
| 2 | Venus | Terrestrial | 108.2 million km | Ancient | 0 |
| 3 | Earth | Terrestrial | 149.6 million km | Ancient | 1 |
| 4 | Mars | Terrestrial | 227.9 million km | Ancient | 2 |
| 5 | Ceres | Dwarf planet | 413.8 million km | 1801 | 0 |
| 6 | Jupiter | Gas giant | 778.5 million km | Ancient | 95 |
| 7 | Saturn | Gas giant | 1.43 billion km | Ancient | 146 |
| 8 | Uranus | Ice giant | 2.87 billion km | 1781 | 27 |
| 9 | Neptune | Ice giant | 4.5 billion km | 1846 | 16 |
| 10 | Pluto | Dwarf planet | 5.91 billion km | 1930 | 5 |
Planets are ranked by orbital period (the sidereal period — one full revolution around the Sun relative to the fixed stars), from shortest to longest. Data comes from NASA's Planetary Fact Sheet, JPL Solar System Dynamics, and the IAU Minor Planet Center. All eight IAU-recognized planets are included, plus the two dwarf planets with the longest confirmed orbital periods (Pluto and Eris). Ceres, Makemake, and Haumea are excluded for clarity; their orbital periods fall between the values listed here.
This list includes the two largest dwarf planets — Ceres and Pluto — to make a full top 10. Ceres is the closest dwarf planet to the Sun, and Pluto is the most massive known dwarf planet. Eris has an orbital period of 559 Earth years, even longer than Pluto, but is excluded because its orbital period is so extreme it would dominate the scale.
Eris, the most distant known dwarf planet, has an orbital period of approximately 559 Earth years. It was excluded from the main 10 because its extreme distance would compress the visual scale of the other entries. Its orbit is also highly eccentric (e = 0.44), taking it from 37.9 AU to 97.6 AU from the Sun.
Earth years are the standard astronomical unit for comparing planetary orbital periods, because one Earth year is a familiar reference point. The same data is also available in Earth days — for example, Mercury's orbital period is 88 days, and Neptune's is 60,190 days.