About what percentage of the Earth's surface is water?

The story behind the answer

About 70% of Earth’s surface is covered by water—mainly the interconnected world ocean—leaving about 30% as land. That’s why Earth appears so blue from space and is often called the “Blue Planet.” The oceans, seas, and marginal waters dominate the surface area, making 90% far too high and 50% or 30% too low.

Interesting context: while water seems abundant, about 97% of it is salty. Only about 3% is freshwater, and most of that is locked in ice or deep underground; less than 1% is readily accessible in rivers and lakes. Memory tip: think “7 continents, ~70% water”—seven and seventy stick together, reminding you that roughly seven-tenths of Earth is ocean.