This article contains a list of countries by length of coastline, in kilometers.
Measurements of the length of a coastline behave like a fractal, being different at different scale intervals (distance between points on the coastline at which measurements are taken).
The smaller the scale interval (meaning the more detailed the measurement), the longer the coastline will be.
[a] This "magnifying" effect is greater for convoluted coastlines than for relatively smooth ones.
[1] Non-sovereign areas are listed in italics.