Fillet Weld Strength & Cost

A fillet weld is sized by its leg because that is what a gauge measures, but it is checked on its throat — the shortest distance through the weld — which for an equal-leg fillet is 0.707 z. Capacity per unit length is that throat times the allowable stress your design code gives you, and the total is that times the effective length, doubled if you weld both sides. The allowable stress is an input here and nothing is stored: the right value depends on the code, the electrode, the direction of loading and the joint, and those tables belong to the standards, not to this page.

The same triangle gives the consumable. A fillet’s cross-section is ½ z² plus whatever convexity you actually deposit, so weld metal grows with the *square* of the leg: going from 6 mm to 8 mm is not a third more metal, it is nearly double — which is why oversizing a fillet is the most expensive habit in a fabrication shop. Divide the deposited mass by the deposition efficiency for the consumable you have to buy, by the deposition rate for arc time, and by the operating factor for the share of a welder’s shift it really takes. That last one is usually the largest number in a welding cost and the one nobody measures.

Statically loaded, uniformly stressed, equal-leg fillets on a joint somebody has already sized. There is no weld group analysis here, and that matters: a bracket loaded eccentrically puts far more into one end of a weld than this average suggests. No direction-of-loading factor, no fatigue category, no residual stress or distortion, no base-metal check and no throat reduction for a gap in the fit-up. Gas, power, grinding, fit-up, positioning and inspection are outside the cost; on most real jobs they are larger than the wire. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.