at the end of the day it depends on the individuals response to aspirin as an analgesic, and also, how severe the pain is. as well, of course, as to the cause of pain, and presence of inflammation. in general, a person will be given 150-300mg of aspirin in one dose to produce relief...although up to 1000mg is used as i recall (dont do this at home, hospital only) so for some people, generally smaller people who are responsive to it, yeah, 100 will work. for others, well...its like having skittles