How big is neptune?

The radius at the poles is 15,125 miles (24,341 km), slightly smaller than the equatorial radius of 15,388 miles (24,764 km). The average diameter across the planet is 30,598 miles (49,244 km), almost four times the diameter of Earth. A trip around Neptune's equator would cover 96,129 miles (154,705 km). read more

Neptune is the fourth largest planet in terms of diameter, making it the smallest in physical size of the gas giants. The average distance from the center of the planet to its surface is 15,299 miles (24,622 kilometers). But like most spinning bodies, Neptune's rotation causes it to bulge slightly around the equator. read more

The surface area of Neptune is 7.64 x 10 9 km 2. That’s 15 times as much surface area as Earth; of course, Neptune doesn’t have a solid surface, so you wouldn’t want to live there. The mass of Neptune is 1.02 x 10 26 kg. Again, for comparison, that’s the equivalent of 17.1 Earths. read more

Neptune's equatorial radius of 24,764 km is nearly four times that of Earth. Neptune, like Uranus, is an ice giant, a subclass of giant planet, because they are smaller and have higher concentrations of volatiles than Jupiter and Saturn. read more