Portugal-Spain border English mathematician Lewis Fry Richardson found the coastline paradox when he noticed that Spain measured the length of its border with Portugal to be 987 km (613.3 miles), and Portugal reported it to be 1,214 km (754.3 miles). (more) coastline paradox geography Ask the Chatbot a Question More Actions Share Share Share to social media Facebook X URL https://www.britannica.com/science/coastline-paradox Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article.

　　External Websites Ask the Chatbot a Question Written by Laura Payne Laura Payne is a freelance writer whose work covers many topics. She is a former Wayne State University linguistics instructor. Laura Payne Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Nov. 17, 2025 •History Table of Contents Table of Contents Ask the Chatbot coastline paradox, a mathematical concept showing that the measured length of a coastline is not a definite quantity but varies based on the scale of measurement used and the level of detail that scale reveals. The smaller the measuring scale, the more details are revealed and the longer the measured length will be. This paradox occurs because coasts do not have straight lines; they have turns, curves, and promontories shaped by features such as bays,...

　　Continue reading with Britannica Premium The trusted destination for facts and information 7-Day Free Trial, No Ads, Unlimited Access Subscribe Today