How big are countries really? A Mercator vs globe lesson
Ask a class whether Greenland or Africa is bigger, and many students will hesitate. On the world map they see most often, the two look about the same size. In reality Africa is about 14 times larger. This lesson lets students discover the gap themselves with a globe and a true size tool, and then explains why so many maps get it wrong.
Suggested age: 10–14 · Time: about 40 minutes · Links: all lessons · for schools · true size tool
Learning goals
By the end of the lesson students can:
- Explain that every flat map changes the shape or size of some places, because a sphere cannot be flattened without stretching.
- Explain that the Mercator projection makes land look bigger the farther it is from the equator.
- Use country areas to compare real sizes.
- Say what the Mercator map is good for, and when a globe or an equal-area map is better.
What you need
- The globe at earthglobe.app on a projector (press Classroom mode) or one device per pair.
- The true size tool.
- A world map on the Mercator projection. Many classroom posters use it, and many online street maps use a version of it (Web Mercator) when you zoom all the way out.
Step-by-step globe activity
- Guess first (4 min). Show the Mercator world map. Ask students to rank these by size, largest first: Greenland, Africa, DR Congo, Australia. Write the class's guess on the board.
- Look on the globe (6 min). Open the globe and switch to Borders. Search for Greenland, look at it, then drag the globe slowly south to Africa without zooming. Ask: "Does Greenland still look as big as Africa?"
- Read the numbers (6 min). Tap Greenland and note its area from the country card. Then tap DR Congo. Which is larger? Students write both areas down.
- Lay them on top of each other (6 min). Open the true size tool and choose Greenland and DR Congo. The tool draws both countries at the same scale, without stretching. Then try Greenland against a few African countries of your choice.
- Why does the map lie? (8 min). Explain the story: Gerardus Mercator published his map in 1569 for sailors. On his map, a straight line is a constant compass direction, which made navigation simpler. To do that, the map stretches the world more and more towards the poles. Show the table below and ask: "Why does Mercator's map stop before the poles?" (The stretch becomes endless there.)
- Test other pairs (6 min). In pairs, students check one claim each with the globe or the true size tool:
- Madagascar looks about as big as Great Britain on a Mercator map. Which is bigger?
- Greenland or Australia: which is bigger in reality? Check how they look on the Mercator map too.
- Pick any country near the equator and any country far north. Compare them.
- Wrap up (4 min). Go back to the class's ranking from step 1 and correct it together.
How much does Mercator stretch?
On a Mercator map, the area of land is stretched by more the farther it is from the equator:
| Latitude | Area on a Mercator map compared with reality | Example places |
|---|---|---|
| 0° | 1× (true size) | Ecuador, Kenya, Indonesia |
| 30° | about 1.3× | Egypt, Texas |
| 45° | about 2× | Northern Italy, Oregon |
| 60° | about 4× | Oslo, Helsinki, southern Alaska |
| 70° | about 8.5× | Northern Norway |
| 80° | about 33× | Svalbard, far north Greenland |
Real sizes to compare
| Place | Area |
|---|---|
| Africa (whole continent) | about 30.4 million km² (11.7 million sq mi) |
| DR Congo | 2,344,858 km² (905,355 sq mi) |
| Greenland | 2,166,086 km² (836,330 sq mi) |
Greenland is a territory of the Kingdom of Denmark. It is included because it is the classic example.
Questions for students
- Why can't a flat map show every country at its true size and shape?
- About how many times bigger is Africa than Greenland?
- Which is bigger, Greenland or DR Congo?
- Why did sailors like the Mercator map?
- On a Mercator map, how much is land at 60° north stretched in area?
- If you wanted a map that shows true sizes, what could you use instead?
Answer key (for the teacher)
- The Earth is a sphere. You cannot flatten a sphere without stretching or tearing it, so every flat map changes either sizes, shapes, distances or directions somewhere.
- About 14 times.
- DR Congo (2,344,858 km² against 2,166,086 km²).
- On a Mercator map, a straight line is a constant compass direction, so sailors could draw a straight course and follow one compass bearing.
- About 4 times.
- A globe, which keeps both size and shape, or an equal-area map projection such as Equal Earth or Mollweide, which keeps areas correct but bends shapes.
For step 6 pairs: Madagascar is more than twice as big as Great Britain. Australia is far bigger than Greenland (Australia: 7,692,024 km² on the country card).
Optional extension
Map debate. Many online maps still use a version of Mercator, because it works well when you zoom in to streets. In 2025 the African Union backed a campaign to use the Equal Earth map instead of Mercator, so that Africa is shown at its true size. Older students can discuss: which map should a school use on its wall, and why? Then explore the night side of the Earth in night lights: where people live.
Frequently asked questions
Why does Greenland look as big as Africa on maps?
Most web and wall maps use the Mercator projection, which makes land look bigger the farther it is from the equator. Greenland is so far north that it is drawn many times too large. Africa is about 14 times bigger.
What is the Mercator projection?
A way of drawing the round Earth on a flat map, published by Gerardus Mercator in 1569 for sailors. It keeps compass directions and local shapes correct but exaggerates the size of land far from the equator.
Which map shows the true size of countries?
No flat map gets everything right. Equal-area projections keep every area correct but bend shapes. A globe keeps both.