A small eukaryotic cell is about 10 μm (10 x 10^-6, or 10^-5 m.) in diameter.

Your body has 10 trillion (10¹³) cells (chapter 15).

Total length of your cells lined up end-to-end:
(10¹³) x (10^-5 m.) = 10⁸ (100 x 10⁶) m.

The earth's circumference is 40 million (40 x 10⁶) m.

100 / 40 = 2.5: your smallest cells can wrap around the earth 2.5 times.

This is a conservative estimate; most of your cells are bigger than 10 μm - up to 100 μm.

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