Geography experts agree on which country boasts the most coastal mileage. With shores extending along the Atlantic, Arctic, and Pacific oceans, Canada claims the title of world's longest coastline. While that fact isn't disputed, the exact size of the country's coasts is harder to pin down.
Depending on the source you reference, the length of Canada's shorelines varies by tens of thousands of miles. World Atlas and World Population Review both give a total length of 202,080 kilometers, or 125,567 miles, while Canada's national statistical office lists 243,042 kilometers, or 151,019 miles of coastline.
This discrepancy comes from the phenomenon known as the Coastline Paradox. Measuring coasts isn't as simple as determining the length of a country as the crow flies. The borders where the land meets the ocean don't form a straight line. Instead, they comprise bends and nooks that change in small ways over the course of a day and in bigger ways over years. Measuring shorelines in smaller units technically results in more accurate numbers, but they're also impossibly large and not very practical in the real world.
This is why cartographers choose to look at coastlines on a bigger scale. Even so, two cartographers working with different units of measurement—say miles instead of units of 100 miles—will get different numbers for the same piece of seaside land.
We may never know the exact length of Canada's coast, but we can still say that it's the largest in the world. That's because we can compare its coastline to those of other countries measured on the same scale. All common units of measurement used by cartographers rank it above other countries with impressive coastal real estate, such as the runner-ups Indonesia, Norway, and Russia. Measuring these places on a molecular level may yield different results, but that's not a project experts are eager to embark on anytime soon.