Canadian Welding Bureau (CWB) Level I Practice Exam

Measuring the leg length directly at the weld toe using a fillet gauge or calipers gives you the true size of each leg of a fillet weld. The leg length is defined by how far the weld extends along each leg from the toe where the weld meets the base metal. A fillet gauge is designed with notches that correspond to standard leg lengths, so you can match the weld to the correct size, or you can use calipers to measure from the toe to the root along each leg.

Measuring at the root isn’t appropriate because the root is just the back edge of the weld where it starts, and it doesn’t represent how long the weld extends along the face of the joint. The throat thickness is a different dimension entirely, related to the distance from the weld root to the weld face, and doesn’t tell you the leg length. Estimating by eye is not reliable for meeting code or specification requirements.

So, using a fillet gauge or calipers at the toe of the weld provides an accurate, code-aligned measurement of leg length.