It's informal and colloquial, but in the U.S. it is correct. There is a completely different word "deadbeat," which can mean "a person who doesn't pay his debts," but the two uses would never be confused. Here are various ways of saying the same thing. Standard: "I'm exhausted." Informal and colloquial: "I'm beat." "I'm dead on my feet." "I'm dead tired." "I'm pooped." "I've had it." "I'm all in." After reading Brian and Matt, I did a search just to make sure I wasn't wrong, but I'm not. I was able to find many examples of use: "Can't this wait until tomorrow?" Scott asked in a hoarse voice. "I'm dead beat."--U.S. novel, 2009 "I'm sorry, girls, but I'm dead beat. And you don't want a dead body on your hands at this late hour, now, do you?” U.S., 2013 ""Yes," I reiterated, "I'm going home, but not on this train. I'm dead beat."--Loren Eiseley, U.S., 1975 "Take the saddle off my horse and put 'er up," groaned Shorty. "I'm dead beat!"--Max Brand, U.S., 1922 “I’ll tell all that later,” I said. “I’m dead beat. I’m a rag.” --H.G. Wells, "The First Men in the Moon," confirming this was also Victorian British usage.

"dead beat" is a derogatory term used for someone that is lazy, shiftless, and does not own up to their responsibilities.... "He is a dead beat dad" (He refuses to pay his child support to help his children)

Hey! No, you shouldn't do that. "Deadbeat" means "a lazy person who avoids their responsibilities". What I think you mean to say is "dead tired" - as in: "I'm dead tired." This is perfectly acceptable. I hope this helps - happy studying! Matt

Further to the above, you can also use the word "beat" (although probably more in US English). You can say, "I'm beat!" - meaning you're tired and finished what you were doing. Now, despite it not being common, you CAN say "I'm dead beat" to describe that you're exhausted. This is correct. However, I would avoid it, as it may sound like you're saying "I'm a deadbeat", which can be a form of self-flagellation! ;)

Wrong