In the flat position, the base metal provides support for the molten pool of weld metal. Therefore, this position provides for the fastest deposition rate and the most economical weld. Welding in the horizontal position is similar, but slightly less efficient. Welding in the vertical or overhead position requires special skills and consumables to maintain the integrity of the molten pool against the effects of gravity.

Because the volume of weld metal in a fillet weld is proportional to the square of the weld size. A 1/2-in. fillet weld uses four times as much weld metal as a 1/4-in. fillet weld of the same length. Because the cost of welding is essentially proportional to the volume of weld metal, the most economical fillet-welded detail will result when the least possible fillet weld size is used. Accordingly, it is common practice in welded joint design to select fitting and weld length to minimize fillet weld size, when possible. Additionally, smaller welds reduce the possibility of warping and distortion due to heat input.

Fillet welds do not generally require beveling and similar base metal preparation. Groove welds usually do require cutting a bevel. As a result, fillet welds less than about ¾ in. are generally more economical to make than equivalent groove welds. Thus, fillet welds are preferred for smaller sizes, and grooves are typically more economical for larger sizes.