Minimum Fillet Weld Size — D1.1:2025 Table 7.7
Per D1.1:2025 Table 7.7, minimum fillet weld size is determined by the thicker part joined (low-hydrogen processes) or thinner part (non-low-hydrogen). Four thickness ranges: under 1/4 in → 1/8 in; 1/4 to under 1/2 in → 3/16 in; 1/2 to under 3/4 in → 1/4 in; 3/4 in and over → 5/16 in.
| Thickness of Thicker Part Joined | Minimum Fillet Weld Size |
|---|---|
| To 1/4 in [6 mm] (exclusive) | 1/8 in [3 mm] |
| Over 1/4 in to 1/2 in [6–12 mm] (exclusive) | 3/16 in [5 mm] |
| Over 1/2 in to 3/4 in [12–20 mm] (exclusive) | 1/4 in [6 mm] |
| Over 3/4 in [20 mm] | 5/16 in [8 mm] |
Source: D1.1:2025 Table 7.7 — Note (a): for non-low-H processes without Clause 6.8.4 preheat, size governs by thicker part and single pass is required. Note (b): weld size need not exceed thickness of thinner part. Note (c): for cyclically loaded structures, 3/16 in minimum regardless of thickness.
Which thickness governs depends on your process and preheat procedure — D1.1:2025 Table 7.7 footnote (a). Clause 6.8.4 = qualified preheat procedure, not just using preheat.
FAQ
More Welding Tools
AWS D1.1/D1.1M:2025 (current edition)