Originally Posted by FFNoMore?

For each flight United shows a seating chart that shows the assigned seats.

Is there any way to tell how many seats are actually sold for each flight? I know in the past there was a 3rd party that used to show the seat inventory for each flight.

Originally Posted by WIRunner

Expert flier is your best bet; it is a paid subscription though.

The seatmap and actual seats sold actually have no bearing on each other.

Originally Posted by FlyingProf

The seat bucket counts are the best you can do -- they tell if you there are more or less than 9 seats still to sell at each available fare bucket ... when Y is under 9, you know the flight is damn near full. AS more buckets hit zero on any given flight, you are getting closer and closer to a fully sold plane. That being said, it's not perfect as the airline sometimes blocks some seats which it will later unblock -- but it does give you a sense.