I've heard from various people who wear the three percenter things on their hats and cars that only three percent of the colonists actually took up weapons to fight the British during the American Revolution. Though they had plenty of supporters, only a very small number of the total population actually fought. Is this true?
It was probably more than that.
This site:
http://www.shmoop.com/american-revolution/statistics.html
says 6.5%
That may be too many. Here is an estimate:
At the height of the war there were said to be 80,000 US troops (continentals and militia)
http://www.shmoop.com/american-revolution/statistics.html
If we estimate that on average, however, throughout the 8 years of war, 30,000 Americans were in the continentals or the militia, and that they served on average two years, this would make 120,000. Plus, the casualties would have needed to be replaced. These were about 6,000 killed, 8,000 wounded, 10,000 died of disease, 18,000 captured by the British. Or about 42,000.
http://www.shmoop.com/american-revolution/statistics.html
Add that to the 120,000 and you get circa 162,000 who took up arms.
The population of the 13 colonies was about 3m. So, this would give 5.4%.
If you included the circa 55,000 Americans who served on privateers during the war, this might go up to circa 7.2%
If you consider that the the free men of military age in the population might have been only 1 in 5 (especially as a fair proportion of the population were slaves), then, of the circa 600,000 free men of military age something like 1/4 - 1/3 might have taken up arms.