Neptune IS bigger than Earth.
Neptune is larger than Earth in volume, diameter, and mass.
Neptune versus Earth Diameter
With an equatorial circumference of 96,129 miles, Neptune is 3.8647 times larger than the Earth. ["Neptune Fact Sheet." NASA]
Neptune versus Earth Volume
With a volume of 15,000,714,125,712 mi3 , Neptune is 57.723 times larger than the Earth. ["Neptune Fact Sheet." NASA]
Neptune versus Earth Mass
With a mass of 1.0241 x 1026 kg, Neptune is 17.148 times larger than Earth. This is interesting because Neptune is a gas planet, but it still weighs more. ["Neptune Fact Sheet." NASA]
Can You See Giant Neptune?
Neptune is not visible to the naked eye. When viewed through a telescope, Neptune appears bluish green due to its composition of methane. The fact that it has a vivid blue tint suggests that it may be composed of an unknown component. ["Solar System Exploration: Solar System 101." NASA]
How Does Neptune's Size Affect Orbit?
The planet's orbit is just as large as its size. It takes 164.791 Earth years for a single year to pass on Neptune. However, due to its faster rotation, at 16.11 hours, Neptune has fewer hours in a day than Earth. ["Neptune Fact Sheet." NASA]
Does This Size Affect Surface Gravity?
While Neptune is substantially larger than Earth, its surface gravity of 36.6 ft/s² is relatively the same as Earth. According to NASA if you weigh 100 pounds on Earth you would weigh 114 pounds on Neptune.