Water in true scale
Oceans and drainage basins are among the largest structures on Earth's surface, yet maps make water easy to treat as background. Estimate the scale first, then compare your answer with the data.
Water covers about 71 percent of Earth's surface. Maps, however, emphasise borders and land names while leaving oceans as largely unlabelled background. That layout makes true proportions difficult to judge by eye.
Each topic below starts with your estimate. Set the slider, then reveal a result tied to named sources. You can immediately see how closely your intuition matches the measurement.
Pick a topic and test your intuition
The Pacific versus all land combined
On a Mercator map, the ocean is easy to treat as background. In reality, the Pacific alone is larger than all continents and islands combined.
Guess and reveal →02The Amazon basin and the European Union
A river's scale is not defined by channel length alone. The Amazon drains an area larger than the entire European Union. Its basin is comparable in size to a continent.
Guess and reveal →03Baikal and all the Great Lakes
The Great Lakes cover nearly a quarter-million square kilometres on a map. Baikal looks modest beside them, yet it holds more fresh water than all five combined.
Guess and reveal →Explore every lake on its own
Every lake featured in the quizzes has a profile with its outline, depth, volume, and sources. The catalog shows why surface area alone cannot tell you how much water a lake holds.
Water in true scale: questions and answers
Water covers about 71 percent of Earth's surface, chiefly in the oceans. The Pacific Ocean alone is larger than the combined area of all land on the planet.
The Mercator projection greatly enlarges areas at high latitudes. A typical world map also splits the Pacific at two edges, making it difficult to see as one continuous ocean.
Every comparison names its sources and data year. We use material from organisations including NOAA, USGS, the US EPA, UNESCO, Eurostat, and Encyclopædia Britannica. The tools and page copy use the same figures.