|Paul, Brindza. How Many Atoms are in the Human Head? Jefferson Lab. May-June 2006.||"A pound is 454 grams so a 10 pound human head is 4,540 grams."||4.5kg|
|Yee, Danny. Average Human Head Weight. Danny Yee. May-June 2006.||"An adult human head cut off around vertebra C3, with no hair, weighs somewhere between 4.5 and 5kg, constituting around 8% of the whole body mass."||4.5kg-5kg|
|Goldstein, Jonathan P. Goldstein Helmet Study. Biker's Rights. May-June 2006.||"The weight of the human head is 8-12 pounds while the average weight of the helmet used in our sample is 2.7 pounds."||3.6kg-5.4kg|
|Item from Budget Request 2001 (The BBC -- Boy Band Collider). Ryerson Astronomical Society. May-June 2006.||"A human head weighs about 5kg; and there are approximately 2 × 10^26 atoms in a human head."||5kg|
|Jerry Maguire. Dir. Crowe Cameron. Perf. Tom Cruise [Jerry], Cuba Gooding Jr. [Rod], Renée Zellweger [Dorothy], Jonathan Lipnicki [Ray]. Sony Pictures, 1996.||"Ray: D'you know that the human head weighs 8 pounds?"||3.6kg|
The typical mass of a human head is about 5 kilograms, significantly larger than what the movie "Jerry Maguire" suggests, a mere 3600 grams. This result probably puts most heads at roughly seven percent of the person's body mass. While the movie was incorrect on the average head, this by no means excludes one from having a head of that size. According to the results, people can have a head as light as only 3500 grams, and those of us with larger craniums can weigh in at over 6300 grams. As the human brain weighs roughly 1500 grams it is likely that a larger head will be no more intelligent than a smaller head but rather just belongs to a larger person. All that extra weight can come from just a plain larger skull, the muscles needed to support it, and other fluids in the head. Some believe that certain thoughts weigh more than others, and research will most certainly be done on this topic in the future.
In order to arrive at a mass for the human head many interesting methods can be used. From the obvious Archimedean approach of dipping your head in a bucket and merely assuming the density of your head is that of water, to the plain bizarre of rotating yourself in space and cutting off a limb to observe the change in the center of gravity. However it is probably safe to say that the most common method is simply throwing the head of an old cadaver on a scale.
Dmitriy Gekhman -- 2006