What is Earth curvature?

The Earth is round, so its surface curves away below a straight, level line. Over a short distance the curve is too small to notice, but over many kilometers it hides things: a ship far out at sea loses its hull from view first, and across a wide lake the lower floors of buildings on the far shore can be hidden. How much is hidden depends on how far away something is and how high your eyes are above the surface.

Tool description

This tool works out what the Earth's curvature hides. Enter the distance to an object and the height of your eyes above the ground or water, in metric or imperial units. It gives the curvature drop over that distance, the distance to your horizon, and how much of the object is hidden below the horizon. A diagram shows what each value means.

Features

  • Curvature drop: how far the surface falls below a level line over the distance
  • Horizon distance: how far away the horizon is from your eye height
  • Hidden height: how much of a distant object is hidden, counted up from its base
  • Metric (km and m) or imperial (mi and ft) units, and switching converts the values you entered
  • Picks cm, m, or km (in, ft, or mi) to fit the size of each result
  • Runs in your browser