Weight limit for carry on suitcase?

most airlines allow up to 100lbs of luggage for free. I believe it is 2 bags at 50 lbs each. additional bags or added weight will cost small fees. (weight and fees vary per airline, each carrier website will have a listing) An Exception is that Active Duty military is allowed up to 2 bags at 100lbs each, a total of 200lbs.
The maximum weight is actually different for each airline. But South West is 50lbs. I think that would be a pretty heavvy suitcase, so you PROBABLY don't have to weigh it! Because worst case scenario, you would have like, some instrument er something and it's too heavy!