how large can a blood clot get?

First off, if a person got a blood clot the size of a basketball, I assume that they would most likely be dead.  Now with a little problem I had with urinating blood and blood clots after sex, I have passed blood clots that where paper thin almost, I have passed clots anywhere from smaller than a pea to almost he size of a 50 cent piece. Now internally I am not to certain how big they can truly get in the non lethal variety ( not saying there not lethal in the first place ) I would say smaller than a pea anything bigger may be a serious problem.