Thanks for the metric number line and how to convert two ways. Assuming an adult has 5,000 mL of blood, and each mcL has about 8,000 white blood cells, I calculate 40 billion white cells in the bloodstream alone (more outside). 5,000 mL x 1,000 = 5 million mcL blood x 8,000. Is that calculation correct? (mcL = microliter)