I am looking to size a generator for my house (emergency only) I want to size it as a minimum to be able to run my well pump which has a double 50 amp breaker (240 v). What is the max amps the pump can pull based upon that breaker... is it 50 amps or 100 amps.

You don't need a generator for your freezer or refrigerator.. or anything else in your house... just the well?

... at 240V the breaker will trip at 50A...

Be advised you cannot now say that you need a 50A, 240V generator...
The appropriate genset size will likely be at least 50A x 125%...
The genset sales people will size and make recommendation for you...
If you know a good electrician I would rather trust him than a salesmen...

A well on a 50A breaker? Something is not right.

A well on a 50A breaker? Something is not right.

Maybe it supplies the water tower for a small town.

A well on a 50A breaker? Something is not right.
My thoughts exactly.

Nasran, do you know the horsepower of your pump? You can't really just go off the breaker amperage.