Focal length of lenses

Pretty much, a " standard lens" is the same as the diagonal measure of the film. So,35mm is 50mm(a bit long really, 42mm is about right), 80mm for 2 1/4 square, 4x5 is 160mm (roughly 6.3") 5x7 is 210mm, and 8x10 is 400mm (12").
Wide angle equivalents to 35mm on 35mm, 4x5 = 100mm (4") and 8 x 10 = 210mm (8.3")
These are just rough numbers, not exact.
If you need a wider angle, and are using a digital, consider taking 2 overlapping pictures, and using stitching software to put them together. Works like a charm, most of my "Fine Art" photos are done this way. Gets the wide angle I need, and the high resolution for large prints. I often stitch them in a 6 wide by 3 high array, so I can make 48" prints from an 8 Megapixel camera.