Canada has the longest coastline in the world, measuring over 243,000 kilometers.

Canada's coastline measures 243,042 kilometers. This is more than six times the distance around the entire Earth. Indonesia has the second-longest coastline, but it is much shorter at about 54,716 kilometers.The Canadian Arctic Archipelago is the main reason for this length. This group of 36,563 islands adds over 165,000 kilometers to the total. Baffin Island is the largest of these islands and has a very complex edge filled with deep valleys called fjords.Coastlines are difficult to measure because they are not straight lines. In 1967, mathematician Benoit Mandelbrot explained that coastlines are like fractals. This means they have many small nooks and crannies. If you use a smaller ruler to measure them, the total length actually gets longer because you are counting every tiny curve.Most of these curves were made by giant ice sheets about 21,000 years ago. These heavy glaciers carved deep grooves into the rock as they moved. When the ice melted, the ocean filled these grooves. This created the messy, jagged shoreline that makes Canada's coast so long today.