How long can you sprint at maximum effort?

Considering I haven't done it for a while I have no clue. I ran track in middle school and the first year of High School as a short distance sprinter, and I'd always be winded after the 200m. If I absolutely had to I could sprint a 400m but there is absolutely no way I could do that today.
I could probably still sprint a little over 200m but I'd be absolutely exhausted by the end of it.