What is Fillet Weld Size in Welding?

The size of a fillet weld is typically specified by its leg length. For equal leg fillet welds, the leg lengths are of the largest isosceles right triangle that can be inscribed within the fillet weld cross-section. For unequal leg fillet welds, the leg lengths are of the largest right triangle that can be inscribed within the fillet weld cross-section.

The size of a fillet weld is also specified by its throat thickness. The throat thickness of a fillet weld is the distance from the root to the point where the legs intersect.

What is the standard size of the fillet?

The American Welding Society (AWS) welding code specifies minimum fillet weld sizes for various thicknesses of base metal. For example, when welding 1/4-inch thick material, the minimum size fillet welds should be 3/16 inch. However, for heavier metal thicknesses, such as 5/16 inch and thicker, the minimum size fillet weld should be 1/4 inch.

How do you calculate fillet weld size? Fillet weld size formula

The formula for calculating the size of a fillet weld is:

Size of Fillet Weld (in.) = 0.707 x Thickness of Plate (in.)

For example, if you are welding two pieces of 1/4-inch thick plate together, the size of the fillet weld would be: Size of Fillet Weld (in.) = 0.707 x 1/4 (in.)

= 0.177 or 3/16 inch

What is the minimum size for a 12mm fillet weld?

The minimum size for a 12mm fillet weld is 6mm. This is based on the formula:

Size of Fillet Weld (in.) = 0.707 x Thickness of Plate (in.),

so when welding two pieces of 6mm thick plate together, the size of the fillet weld would be Size of Fillet Weld (in.) = 0.707 x 6mm (in.) = 4.2mm or 3/16 inch.