You're asking for the ratio of Neptune's diameter to Earth's diameter. Here's how to calculate it:

* Neptune's diameter: 49,528 kilometers (30,775 miles)

* Earth's diameter: 12,742 kilometers (7,926 miles)

Ratio: Neptune's diameter / Earth's diameter = 49,528 km / 12,742 km ≈ 3.88

Therefore, Neptune's diameter is approximately 3.88 times larger than Earth's diameter.