i have a queen size futon sofa bed. the long way measures 80'' the back part measures 24'' or 25'' and the?

seat part measures 24'' or 25'' too.
ok, how many cushions do i need? and what should the pillows measure? and possibly where can i buy the cushions for the seat and the back?
dont 4get it measures 80'' long. help. and also i dont want a mattress only cushions.

6 Standard pillows 26X26" (3 x 26 = 78) is the closest size.
http://www.target.com/gp/search/183-4599812-4023252?field-keywords=pillows%2026×26&afid=google&CPNG=Bedding&LNM=pillows_26×26&LID=5306481&ref=tgt_adv_xsgt0521
27X26" would be ideal (3 X 27 = 81 inches) the extra inch will help them fit snugly and you want them to overlap the backrest/seating by an inch or two, the problem is you can't buy pillows in those dimensions unless you had them custom made or make them yourself, even outdoor cushions come in universal sizes-chaise: 21×71", bench: 46×18", cushions: 21×44", same with body pillows. http://www.walmart.com/catalog/product.do?product_id=2128727#Features+%26+Specifications 78×27"

What type of futon mattresses feel more comfortable?

I have a regular folding futon with a thicker mattress (not the really thin kind that usually come with iron framed-futons).

One side is starting to sink in a bit and I think I'd like a new one soon.

I'm looking for one that comfy to sleep on, but doesn't cost much more than $150. Any suggestions on a comfy type of futon mattress?

Thanks : )

I have a futon myself with a very good (aka. expensive) mattress…trust me whichever mattress you get WILL get a crease in the middle assuming you leave it in a couch position most of the time. Also, the really good ones are hard to fold in half (going from bed to couch). We have to remove the mattress, fold the futon, and shove the mattress back into place. With all of this it is a two person job - which isn't what you think of with a futon. So my opinion is get the best one in your price range and try to pull it in and out yourself to see how easy it works. Good Luck!