First let me say that this calculation is probably wrong. But one of Brad DeLong’s One Hundred Interesting Math Calculations asks How Much Blood is there in the World? (How much human blood, that is.) The answer assumes that the average person has about a gallon of blood in them, which is a tad low, I think — it’s more like 9.5 to 10.5 pints per person. But let’s keep it at a gallon. The answer is about 8 × 108 cubic feet of blood, which is less than you might think: as Brad says, “All the human blood in the world could be stuffed into a cube less than one-thousand feet on a side.”
But who can visualize a cube a thousand feet long on a side? As a person with a sociological interest in blood, I like the calculation, but I need to translate it into the standard SI unit of volume applicable to this case, namely the Olympic-size swimming pool. My goal is to do the conversion using only Google.
Brad gives us the 8 × 108 cubic feet number. An Olympic pool measures 50 × 20 x 2 meters, which gives us 2000 cubic meters or 2 × 106 liters. So we have a units problem. But Google knows that 2 × 106 liters is 528,344.102 US gallons. Google also knows that this is equivalent to 706,293.746 cubic feet. And so it will be no surprise to learn that Google has no trouble calculating that 8 × 108 cubic feet divided by 706,293.746 cubic feet is 1,132.6732. Roughly speaking, all the human blood in the world would fit into about eleven hundred Olympic-sized swimming pools.
According to the National Blood Data Resource Center, about 15 million pints of blood are collected each year in the United States. That’s equivalent to just over three and a half Olympic pools. Blood is a renewable resource, of course, in that you make more of it when you lose some. Over the course of a year the U.S. blood system controls the allocation of roughly 0.31 percent of all the blood in the world. Unless the glass of wine I’m having has caused me to make a mistake somewhere.
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