Lumber with more knots costs less, which makes sense. If your project contains a bunch of smaller pieces, you can save money ...

Beams and stringers. Lumber of rectangular cross section, 5 in (127 mm) or more thick and 8 in (203 mm) or more wide, graded with respect to its strength in bending when loaded on the narrow face.

NDS Section 4.3.4 specifies that C r = 1.15. For visually graded sawn lumber joists exceeding 12 inches in depth and 5 inches in thickness the size factor, an adjustment for loss of tensile strength ...