Orbital speed is the object's instantaneous speed at a certain point in its orbit or the average speed of the object through its course. These are the fastest planets in the solar system:
Mercury is the fastest planet in the solar system and has a speed of 87.97 Earth days or 47.87km/s approximately.
Venus orbits around the Sun for 225 days and is the second fastest planet in the solar system.
Earth revolves around the sun in 365 days and has an average speed of 29.78 kilometres per second.
Mars takes 687 days to complete one round of the sun and moves at an average speed of 24.07km/s.
Jupiter is the slowest planet among the five and takes 12 years to complete a solar orbit period with a speed of 13.07km/s.