The planet Neptune is 4 times bigger than Earth is.
While the planet earth is very big and would seem like earth would be the biggest planet it actually is smaller than Neptune.
The planet Neptune has a radius of 15,299.4 miles which means it's 4 times wider than the planet earth.
Basically if the planet earth was the size of a nickle then the planet Neptune would be the size of a baseball.
That is an easy way to compare the size of the two planets.
Neptune is much bigger than earth.