[beenthere]

A load calc would reveal how many CFM each area needs, which would allow you to size he duct work and determine how many supplies you need.

 

[Jacob84]

the bed rooms need 6000 btu each and the main area is 1900btu. how can i go about determining duct sizes and number of drops?

 

[beenthere]

The main area needs 1900? but the bedrooms need 6,000 each?

You select registers that will have the throw you need and a low sound rating at the CFM you need. Generally you limit residential to less then 200 CFM per drop. At 6,000 BTUs it would take an 8" supply for the bedrooms.

You need a real load calc done, and not just guess.