A new hiking trail will soon allow travellers to walk around England's entire coast, but no one knows exactly how long it is. The King Charles III England Coast Path, set to open later this year, will be the longest managed coastal walking path in the world. However, the length of the path is not easily measured, as is the length the coastline it follows. This discrepancy is explained by the differing measurements from various organisations. The CIA World Factbook lists the UK's coastline as 7,723 miles (12,429km), while The World Resources Institute measures it at 12,251 miles (19,716km), a discrepancy of over 4,500 miles (7,242km). This disparity widens further, with estimates ranging from 84,000 miles (135,185km) to an astonishing 95,471 miles (153,646km) according to the National Oceanic and Atmospheric Administration (Noaa). The phenomenon, known as the coastline paradox, applies to virtually all borders, boundaries, and coastlines with particularly jagged, twisting lines.