Gerardus Mercator drew his 1569 world map for sailors, and it was very good at that job. Its side effect: the farther land sits from the equator, the bigger it is drawn. On the map most of us grew up with, Greenland looks about the size of Africa.
Africa covers 30.37 million km². Greenland covers 2.17 million. Africa is 14 times larger, yet on a Mercator map the two look about the same size.
Mercator widens every parallel by 1 ÷ cos(latitude), then stretches north–south to match, so area grows with the square of that factor.
Area factor = sec²(latitude), computed (Snyder 1987). Web Mercator stops at 85.05°, where the factor reaches ×134.
Each circle covers the same patch of Earth. Shape is kept, so the circles stay round, but at 75° Mercator draws one with ~15× the area of the one on the equator.
Tissot-style indicatrix: each circle spans the same ground. Area factors computed from sec²φ. Greenland’s centre sits near 72°N (×10.5).
Ranked by actual square kilometres, Greenland comes nowhere near Africa. The right-hand column shows how much Mercator inflates each one.
Areas: CIA World Factbook; Africa: Britannica. “Mercator ×” = sec² of approximate centre latitude, illustrative.
A straight line on Mercator is a constant compass bearing, ideal for navigation in 1569. Web maps adopted it for the same reason: angles stay true, so street corners stay square.
Equal-area projections keep every country’s size in proportion. Since 2018 the Equal Earth projection has been the main candidate to replace Mercator.
Most people meet the world through one projection. When that map shrinks the tropics and inflates the high north, it shrinks Africa, South America and South Asia, home to billions of people. No flat map is perfect. The fix is to pick a projection that suits the job: Mercator for compass bearings, equal-area maps for comparing places.
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