You have 100 trillion somatic cells (chapter 13), all derived from a single zygote by mitosis.

Each round of mitosis produces 2 daughter cells:

- 10 rounds gives 2
^{10}= 1024 cells, about 1 thousand. - 20 rounds gives 2
^{20}= 1,048,576, about 1 million - 30 rounds gives 2
^{30}= 1,073,741,824, about 1 billion. - 40 rounds gives 2
^{40}= 1,099,511,627,776, about 1 trillion. - 7 more rounds gives 2
^{7}= 128 additional multiplier.

So, your average cell has divided 46-47 times since the zygote stage to reach 100 trillion.

This calculation does not include gametes: eggs and sperm.