How far can you see out to sea? It depends how high above the sea you are. The curvature of the earth means that, on the sea shore at a height of two metres, you can see just 5km or 3 miles.
This calculator works out how far you can see at sea at a variety of locations around the UK coastline, including Plymouth Hoe, the top viewing platforms of Portsmouth’s Spinnaker Tower and Blackpool Tower, the White Cliffs of Dover, Beachy Head, the cliffs near Boulby (the highest sea-cliff on England’s east coast, Great Hangman in north Devon (the highest sea-cliff in England), Conachair on St Kilda (the highest sea-cliff in the UK) and a jet at cruising altitude.
The result tells you the distance of the horizon at sea level. It may also be possible to see the tops of objects that are further away.
When you choose a location, its height above sea level in metres will appear in the lower box. You can also use this box to enter any other height.
Heights are from Ordnance Survey mapping or the websites of the towers in question.