All the blood in the world, and then some

by Kieran Healy on January 30, 2005

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 x 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 x 108 cubic feet number. An Olympic pool measures 50 x 20 x 2 meters, which gives us 2000 cubic meters or 2 x 106 liters. So we have a units problem. But Google knows that 2 x 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 x 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.



Matt 01.30.05 at 4:15 am

Funny you’d mention how much blood it takes to fill a swimming pool. This idea was used nicely many years ago by Alan Moore and Bill Sienkiewicz in their graphic novel on the CIA, _Brought to Light_, to show how many people had been killed in CIA backed operations over the years. Too many swimming pools to bear thinking about, unfortunately.


PZ Myers 01.30.05 at 4:44 am

It’s closer to 1.5 gallons per person, about 5.5 liters, or almost 12 pints.

It still lacks punch, though. I once worked in a cardiac research lab as a low-level flunky, and in that work they were implanting gadgets to measure flow rates in the carotid arteries of large, 150lb dogs (selected because they had roughly the same blood volume as a human being.) Every once in a while these experimental dogs would manage to hook a claw into the gadget when we weren’t looking, and would yank it out. This would result in nearly instantaneous exsanguination.

I mentioned I was the lab flunky. Guess who got to clean up the mess?

Anyway, it meant I got to be up close and personal with the amount of blood present in one person. I still have unpleasant dreams about me, a mop, and a kennel.

Turning it into numbers of gallons or swimming pools and making huge numbers that we have a hard time imagining is something that actually distances us from the reality, I think. Phrasing it as “cubic feet” is so clean and antiseptic. “Swimming pools” sounds so tame. It’s all so remote and abstract.

A better exercise would be to dump a gallon of milk on your kitchen floor and then try to clean it up. Although even that doesn’t communicate the thickness of the stuff, or the way it gets fibrous as it clots, or the smell. Or that that much blood represents the life and death of a living creature.

I know, I’m being a real downer over what is supposed to be just a simple math exercise…


John Quiggin 01.30.05 at 4:49 am

Australian media have standardised on 1 OSP = 1 Ml, though this only leaves room for about four lanes.


Blar 01.30.05 at 7:05 am

Let’s see, a gallon is 8 pints, multiplied by 6 billion people, gives 48 billion pints of blood in the world. 15 million pints divided by 48 billion pints is a little less than 1/3000. That’s 1/30 of one percent, so about .03% of the blood in the world is controlled by the U.S. blood system in the course of a year. Looks like you got off by an order of magnitude when translating through swimming pools, etc.

Glad I haven’t been drinking red wine while having a calculation & conversation like this one.


Blar 01.30.05 at 7:37 am

Looking back over your calculations, the mistake seems to be in going from gallons to cubic feet. Brad has that 1 gallon = .133 cubic feet, but you have the volume of a swimming pool in cubic feet slightly larger than the volume in gallons. Looks like Brad is right – you should be dropping an order of magnitude.

If there are 4 liters of blood per person and 2 x 10^^6 liters per swimming pool, then the number of swimming pools of (human) blood in the world is about 4 x (6 x 10^^9) / (2 x 10^^6) = 12 x 10^^3 = 12,000 swimming pools of blood. That’s about an order of magnitude larger than what you had.

[note: preview didn’t like my exponentiation signs (^) so I made them double (^^)]


kyan gadac 01.30.05 at 2:10 pm

An emergency medic, in a class I was in, once demonstrated the nature of our perception of blood quantities. He spilled a glass of water on the floor and said “imagine tht’s blood coming from a patient, how much has he lost? The average person would say, pints! heaps! he’s bleeding all over the place. But it’s only 200ml.”


KCinDC 01.30.05 at 3:10 pm

I think the 1.5-gallon figure is for the average adult, but a substantial fraction of the people in the world are children, who may have considerably less. Perhaps Kieran’s 1 gallon isn’t so unreasonable.


lillemask 01.30.05 at 6:03 pm

I suppose this is mostly off-topic, but I always get uncharacteristically annoyed whenever I am reminded that Americans use different units of measurement to the rest of the world.

Despite having been fluent in English the major part of my life and living two years in Great Britain, I still can’t seem to form a mental picture of a gallon.

Strangely, this is the one kind of American chauvinism that upsets me the most.

Not ratifying the Kyoto protocol and undermining the work of the UN and the International Court of Justice are things I can come to terms with, perhaps even understand. Still measuring things in gallons, miles and degrees Fahrenheit? That is just insane.


frank 01.31.05 at 4:21 am


jlw 01.31.05 at 4:27 pm

I think working the calculation the other direction is more impressive.

~6 billion people / ~10,000 pools gives you about 600,000 persons worth of blood per pool. That is, you could drain the population of Fallujah into the White House pool and still have room left over for some Tikritis.


Phersu 02.06.05 at 3:29 pm

The Pool of Blood is also used as a unit in Alan Moore’s comic on the CIA, “Brought to Light”. I do not think it works visually.

For people interested in Blood transfusion in popular culture, there is also that Lois Lane story on

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