How many budles of shingles will it take to roof a 650 square ft building?

What's the pitch of the roof? If the roof area is 650 sq. ft., you will need 21 bundles of shingles up to 30 year, 27 bundles of 35+ year shingles. 30 year or less come 3 bundles to a square, 35+ shingles are 4 bundles to a square (100 sq. ft.). If the footprint of the building is 650 sq. ft., you will need to include the pitch to determine the area of the roof. Hope this helps.