How Far Can You See to the Horizon?

The Horizon Distance Formula

For an observer at height h (meters) above sea level on a spherical Earth (radius R ≈ 6,371 km):

d ≈ √(2Rh) (distance d in kilometers)

Example

Eye height = 1.8 m → d = √(2 × 6371 × 1.8) ≈ 4.8 km (about 3 miles).

Higher vantage points (cliffs, ships' bridges, aircraft) dramatically extend the visible horizon.