Earth’s average orbital speed around the Sun is about 29.78 kilometres per second.
That figure is an average because Earth follows a slightly elliptical orbit rather than a perfect circle. Earth moves fastest near perihelion, its closest point to the Sun, at roughly 30.29 km/s, and slowest near aphelion, at roughly 29.29 km/s.
Earth travels around 940 million kilometres during one orbit, which takes about 365.256 mean solar days—a sidereal year. Its average distance from the Sun is approximately 149.6 million kilometres, or one astronomical unit.
The speed is difficult to picture: at 29.78 km/s, Earth could cover a distance equal to its own diameter in about seven minutes. The seasons are not caused mainly by changes in orbital speed, however; Earth’s 23.4-degree axial tilt is the dominant cause of seasonal sunlight changes.