The countries with the longest coastlines in the world

Ask ten people which country has the longest coastline and most will guess an island nation or vast Russia. The correct answer is Canada, and by an enormous margin. Yet the moment you measure carefully, a simple number turns into a mathematical problem known as the coastline paradox. Here are the countries with the longest coastlines and why every figure is only ever approximate.

Canada plays in its own class

According to the CIA World Factbook, Canada's coastline runs to around 202,080 kilometres. That is more than three times the second-placed country and, on paper, would wrap round the equator five times. The reason lies in the north: the Arctic archipelago is made up of thousands of islands, from vast Baffin Island to tiny rocks, and each one brings its own shoreline. Add up all those crinkled edges and you get a length that defies imagination.

Why islands rule the ranking

Almost every country near the top is one with a lot of islands. A single mainland has a limited coast, but an archipelago multiplies it with every island added. Indonesia and the Philippines are made of thousands of islands, and that is exactly what pushes them up the table. A compact country such as France lands far behind despite touching two seas.

• Canada: around 202,080 km, shaped by the Arctic archipelago.
• Indonesia: around 54,720 km, spread across more than 17,000 islands.
• Russia: around 37,650 km along its Arctic and Pacific shores.
• Philippines: around 36,290 km, an archipelago of over 7,000 islands.
• Norway: around 25,150 km by one measure, many times that once the fjords are traced.

Norway's fjords are the clearest proof

Norway shows the problem like no other country. Draw a smooth line along the outer edge and it comes to only about 2,650 kilometres. Follow every fjord to its inner tip and round each of the more than 300,000 islands and skerries, and the coastline grows to over 100,000 kilometres. The same coast, two numbers, forty times apart. It simply depends on how closely you look.

The coastline paradox

This effect is called the coastline paradox. Early in the 20th century the scientist Lewis Fry Richardson noticed that the length of a border depends on how long your measuring stick is. A shorter ruler picks up more small bays and bends, so the total grows. Britain's coast measures about 2,800 kilometres with a 100 kilometre ruler, but around 3,400 kilometres with a 50 kilometre one.

Benoit Mandelbrot turned this into the basis of his fractal theory in 1967. A coastline is never a smooth line but jagged at every scale: bays hold smaller bays, and those hold smaller ones still. So there is no single true length, only a value for a chosen resolution. That is why the figures differ from one atlas to the next, without anyone having made a mistake.

In CountryRush what counts in the end is not the kilometre figure but whether you recognise the country from its outline, fjords or not. The Daily Trip mixes island nations and mainland giants so you learn to catch both.