Horizon & Line-of-Sight Distance
Calculate how far you can see to the horizon from a given height and the distance at which two objects are visible to each other, free online.
About this calculator
Distance to the horizon d ≈ 3.57·√h km (h in metres) geometrically, or 3.86·√h km including average atmospheric refraction. The line-of-sight between two heights is the sum of their individual horizon distances. A 1.7 m tall person sees about 5 km; from a 100 m tower about 38 km.