What's the dry weight of my skeleton?
January 19, 2012 6:41 AM   Subscribe

Help me calculate: if my dead body were placed in an ossuary, how much would my skeleton weigh when pretty much fully dessicated?

I have no background in medicine, anatomy or anthropology. If you do, can you help me do better than just applying the wildly varying percentages that searching the net gives me? That's only narrowed it down to between 12 and 20%, which is not close enough.

Details: white US male, 46. Height: 5'8" Weight 175. Decent diet with plenty of calcium. History of load-bearing exercise including marathon running. No family history of severe bone loss, etc. I have had one stress fracture in my foot from over-training.

Obviously I'm "overweight" by most standards, so I obviously need to account for that somewhat, even if I settled for some standard percentage to apply to total weight.

And, for emphasis, I'm not talking about the weight of my freshly-dead skeleton, but for my dry old bones.
posted by Mngo to Health & Fitness (12 answers total) 2 users marked this as a favorite
5'8" and 175 pounds is not overweight.

This claims that the human skeleton comprises 30-40% of the total weight of the body, of which half of it is water. So, assume that 15% to 20% of your body's weight.

175 * .15 = 26.25
175 * .2 = 35
posted by dfriedman at 6:46 AM on January 19, 2012

Something like 15-20% of your current weight, according to Wikipedia.

Basically, the human skeleton consists of 30-40% of your body weight--in a normal, non-obese person, I'd imagine--but almost half of that weight is water, both in the bones themselves but also in the marrow they contain. Get rid of that water, and you're down to 15-20% of your normal weight.

Turns out water is heavy.
posted by valkyryn at 6:47 AM on January 19, 2012

Sorry, assume that desiccated bones are 15% to 20% of your body's original weight at death...
posted by dfriedman at 6:47 AM on January 19, 2012

Human body composition, Volume 918, by Steven Heymsfield, Timothy Lohman, ZiMian Wang, and Scott Going p. 291:
As a percentage of body mass, the dry, fat-free skeleton comprises about 3% of the body weight in the fetus and newborn and about 6% to 7% of body mass in the adult.
Also it says that whites have significantly lighter skeletons than blacks, curiously.
posted by XMLicious at 6:53 AM on January 19, 2012

XMLicious, that's a great link.
But if I go with 6% of 175 I get 10.5lbs, or 4.76KG, and that same source you link says a little below that 63YO white males average a skeletal weight of 3.446KG.
Any thoughts on that large variance? I dunno, maybe I should expect to loose 1.3 kilos of bone mass in the next 17 years...
posted by Mngo at 7:26 AM on January 19, 2012

Also, if I'm talking about dried-out bones, should I be looking at the "ash weight" instead?
posted by Mngo at 7:28 AM on January 19, 2012

Well, the "Reference Man" listed in the tables at the back of that book was about your height - 170 cm - and weighed 70 kg, a little less, and his "Dry Skeletal Weight" was 5 kg, so that doesn't seem so far off.

I'm not a scientist or anything but I would expect that skeletal weight probably varies widely like every other measurement, even the percentage of body mass represented by the skeleton.
posted by XMLicious at 8:42 AM on January 19, 2012 [1 favorite]

Hm. I wonder what the definition of ash weight is. If it's completely dessicated bones, or what's left after a body goes through cremation.

Cremation data point: My 5' 11" dad weighed 450lbs when he died. His ashes (not actually ash, but ground up bones) weigh 8lbs. He takes up about 150 cubic inches, which is interesting because a lot of "urn size estimators" say that 1lb = 1 cubic inch.
posted by elsietheeel at 8:47 AM on January 19, 2012

Found the description of the Reference Man:
The Reference Man is a compilation of many research reports and is periodically updated by the International Commission on Radiological Protection. The current Reference Man is between 20 and 30 years of age, weighs 70 kg, is 170 cm in height, and lives in a climate with an average temperature of 10° to 20° C. Reference Man is a Caucasian and Western European or North American in habitat and custom.
posted by XMLicious at 8:48 AM on January 19, 2012

According to wikipedia, bone-ash is mostly calcium phosphate, where as the mineral content of bone sounds like it has substantial amounts of carbonate and hydroxyl, which are probably driven off as CO2 and water vapor in the process of burning. Therefore, I don't think ash weight is what you are after.
posted by Good Brain at 11:47 AM on January 19, 2012

We had a scale at the gym that gave us bone mass, and mine was 6 pounds - shockingly light! Our trainer, more your size, had a skeleton weight of 8 pounds. Those must be dry weights, obviously.
posted by ldthomps at 11:52 AM on January 19, 2012

I still don't consider this fully resolved, but to update, I made several different calculations and went with the amount that looked good in the bucket, which was a little over 10 pounds.

This may change how I plan to dispose of my own corpse, at which point my executors may contact the mods to add a note to the question with the empirical answer. Thanks all!
posted by Mngo at 9:15 AM on September 17, 2012

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