How many gallons of paint does it take to paint 600 square two coats?

well being a two story home not knowing exact size i would tell you bout 20-25 gallons without ceilings go to affordablepainters.biz to get a quote

Figure basically 300 Sq Ft per gallon. This will change depending on how porous the siding is and how many coats you are applying. Paint companies recommend two coats for a first rate job. You may be over or under depending but this is a good rule of thumb. Same for the trim.