Fillet welds are measured by which dimension?

• A. By the throat
• B. By the leg length
• C. By the weld length
• D. By the base metal thickness

Answer: (B)

Fillet weld size is defined by the leg length. A fillet weld forms a triangular cross-section where each leg sits against the surfaces being joined, and the size refers to how long those legs are along the surfaces. The throat, the shortest distance from the weld root to the weld face, matters for strength calculations but isn’t how the weld size is specified. The weld length is the extent of the weld along the joint, which is a separate dimension from the leg size. So, the dimension used to specify a fillet weld in drawings is the length of each leg.