Welding & Joining
Fillet Weld Size & Throat
Calculate fillet weld throat thickness, effective area and load capacity for structural fillet welds per EN 1993-1-8 (Eurocode 3).
Units:
Throat thickness a = 0.707 × leg size s. Minimum fillet weld: typically 3–6mm. Maximum economical: 12mm. Always specify weld quality class on drawings (EN ISO 5817: B, C or D).
a = 0.707 × s | F_Rd = a × L × f_vw,d | f_vw,d = fu / (√3 × βw × γM2)
Input
Leg size s iFillet weld leg size in mm.
mm
Effective weld length iEffective weld length in mm. Subtract 2×s from actual length.
mm
Steel grade iSteel grade determines ultimate strength fu and correlation factor βw.
Loading type iLoad direction relative to weld axis affects design resistance.
Result
Throat thickness a [mm]
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Design weld strength f_vw,d [MPa]
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Weld capacity F_Rd [kN]
—
Capacity per metre [kN/m]
—