Cartograph True Size of Countries (Mercator comparer)

What it is for

Almost every web map uses the Mercator projection. It is great for navigation because it keeps angles and local shapes, but it inflates areas towards the poles: at 60° latitude everything looks four times as big as at the equator, and close to the poles the distortion grows without limit. That is why Greenland looks as large as Africa although Africa is about fourteen times larger.

This tool makes the effect visible. It takes a country outline, moves it to any place on the globe while keeping its real shape and size, and reports three areas: the true area, how big it looks on a Mercator map at home, and how big it looks at the new place. Add a second country to compare true sizes directly.

The outlines are Natural Earth 1 : 110 million (public domain). They are generalised, so small countries and islands are missing and areas differ from official figures by a few per cent.

Worked example

Brazil moved over Central Europe (51, 12):

• True area of Brazil: 8,508,530 km²
• Looks on a Mercator map at home like: 9,059,544 km²
• Looks at the new place like: 27,089,365 km²
• Apparent size change: × 2.99

Brazil straddles the equator, so at home the Mercator map shows it almost at its real size. Put over Germany it looks three times as large.

Russia moved to the equator (0, 40) and compared with Australia gave a true area of 17,019,207 km², an apparent area of 83,047,937 km² at home but only 17,692,607 km² at the equator (× 0.21), and a true size 2.21 × that of Australia. After the move the true area is 17,015,331 km² – the move changes it by about 0.02 %.

How to read the result

True area is the geodesic area of the outline on the WGS84 ellipsoid. The two looks like figures are the planar area of the outline on a Web-Mercator map, converted back to square kilometres at the equator’s scale – what your eye compares on a web map. Apparent size change divides the new by the old apparent area: below 1 the country looks smaller after the move, above 1 larger. True size vs compares the true areas of the two countries.

The map shows the country at home in blue, the moved outline in orange and the comparison country in green. The GeoJSON download contains the moved outline for other GIS tools.

Tips and common mistakes

• Enter countries by English name or ISO code: Greenland, GRL or GL all work.
• The target is the new position of the country’s anchor – the centre of the bounding box of its largest part.
• Moving a country across a pole works on the globe, but the Mercator map cannot show latitudes beyond about 85°; the tool warns you.
• Rotation helps to compare long countries with each other, for example Chile laid along a coastline.
• Compare true areas with the True size vs figure, not with the drawing: on a Mercator map the drawing itself is distorted.

FAQ

Why does the shape change when I move a country north?

On the globe it does not. On the Mercator map it stretches vertically and horizontally by the same factor, so it looks larger and slightly bent.

How accurate are the areas?

The geodesic calculation is exact for the outline; the outline itself is generalised at 1 : 110 million, which typically changes areas by a few per cent.

Why is my small country missing?

Natural Earth at this scale leaves out very small countries and many islands.

Which projection should I use for area comparisons?

An equal-area projection such as Mollweide or Equal Earth. Mercator is for navigation and web tiles.