weight a wood beam will carry

Glulam?
Microlam?
LVL?
Fir?
Spruce?
Pine?
Box beam

Lot's of kinds of wood in this world - all with different peculiarities.

i am planning to use a standard douglas fir beam(solid) that is available from Home Depot.

Engineering advice from an internet site like this with no other information about the design of the house is worth what you pay for it.

A fifteen foot sapn is likely to require a man-made LVL or glulam. You give no details about what it will support. Roof only?
or just taking the bounce out of some floor joists midspan with no actaul loading?
header for three stories above?

Complete plans are necessary for complete answer but a generic rule of themb would call for this beam in fir to be a 4 x 18 or 4 x 16

I brought a coop and the kitchen floor is sloping! What can be causing this? My neighbor has a ceramic floor applied over thinset concrete.Our kitchens are back to back.Could this be causing the sloping or a poor design when building the coop be the problem?

I Have A Hot Tub On A Deck And Need To Support It Deck Is ONLY 2X6X10 Will One 4X6X12 Be Enough

fir 8-10 beam 27 feet long

would like to build a patio cover one end through the roof and resting on top of the wall plate tied to the rafters ( wall is 2x6 - 12 on center ) the patio 13 feet deep ( from the house to the front of the slate deck ) would like to use 4 x 6 x13 beam at 2 foot on center for the 27 foot length . other than the roofing no other weight on the roof are the beam ok to use ?

each beam to carry 260 lbs

each beam will carry 260lbs.