Is lung surface area a tennis court?

No, this is usually an exaggerated analogy. A commonly cited estimate for an adult’s alveolar lung surface is about 70 m²; research models vary, with examples around 57–102 m² depending on definitions and assumptions. The official doubles playing court measures about 23.77 × 10.97 m, or 261 m². Even 70 m² is roughly one quarter of that court, and the full facility with safety run-offs is larger still. It is more accurate to say the lungs have a large, folded gas-exchange surface—not the area of a tennis court.