how to calculate header requirements

[George P.]

I have a load bearing wall between a living room and a kitchen that I'd like to open.  I want to put a large window type opening that might be as big as 8 ft x 4ft high. 

is there a rule of thumb or website where I can enter the variables and find out what size beams I need? 

any suggestions? 

[Aaron McGinnis]

Originally posted by @Chad Caldwell:

Double 2x12 will be plenty. This link has good info.

http://www.anthonyforest.com/assets/pdf/sfpa-heade...

Chad - While well-meaning, your advice is potentially dangerous. You don't know enough about the problem to provide a safe solution. What if this is a first floor of a multistory building? What if there's a concentrated roof load? Did you take into account snow load or seismic requirements? ... not to mention that we don't know the width of the house.

To the original poster - removing a load wall is a nontrivial operation with potentially great risk to yourself, your workers, and the occupant of the house. Candidly, if you need to ask this question you need to be seeking real-world help in the form of a certified engineer or competent contractor.

The resources you're looking for start in the international residential code book. If your situation exceeds the recommendations of the code book, you're going to be looking at manufactured header material - which are sized either by an engineer or according to specific manufacturer's guidelines. If you're dealing with wacky compound loads, you need to be talking to an engineer... period.