How to use Weld Strength& Fillet Weld Sizing Verification Calculator
- Enter Welded joint configuration & load type and adjust the options as needed.
- Run the tool and inspect its results, evidence and limitations.
- Copy or download the result, then verify it against the actual website, source data or business records.
Try a concrete example
For a double lap fillet welded joint carrying tensile working load F=60.0 kN across two symmetric fillet welds (120mm each, total length 240mm): using AWS E70XX/ER70S-6 filler metal (tensile 485 MPa) under AWS D1.1 (allowable shear 0.30 x 485 = 145.5 MPa). With a trial leg size a=8.0 mm (throat t_e = 0.7071 x 8.0 = 5.66 mm, weld throat area 1357.6 mm²), working shear stress is only 44.2 MPa, yielding a safety factor of 3.29 (well exceeding the 1.50 design threshold). Maximum load capacity reaches 197.5 kN with minimum required leg size of only 3.6 mm.
How to interpret results
Welded joints are critical load-bearing connections in structural frames, heavy machinery, pressure vessel saddles, and bridges. Fillet welds fail primarily in shear across the 45° effective throat, regardless of global tensile or bending load. An undersized weld suffers catastrophic shear tearing, while an oversized weld causes excessive heat input, HAZ embrittlement, and weld distortion. This tool checks throat geometry and code stress limits.
Frequently asked questions
What is the difference between fillet weld leg size and effective throat thickness?
Leg size (a) is the length of the right-angle triangle legs measured from joint root to weld toes using a mechanical weld gauge. Effective throat (t_e) is the shortest distance from the root to the hypotenuse face. For a standard 45° equal-leg fillet weld: t_e = a · cos(45°) ≈ 0.707 × a. Strength calculations are strictly based on effective throat area, not leg size.
Why are fillet welds evaluated primarily on shear stress under all load directions?
Stress tensors on asymmetric fillet welds show pronounced stress concentrations along the 45° throat plane. Metals have substantially lower shear yield strength than tensile yield (~0.577 x tensile per von Mises). Over 99% of fillet weld failures initiate as shear tears along the throat. Consequently, AWS D1.1 and AISC adopt the conservative assumption that all forces are resolved into shear on the throat.
What does 70 represent in AWS E70XX and how should it match base metals?
In AWS designations, 'E' denotes electrode and the first two digits designate minimum guaranteed tensile strength in ksi (kips per sq inch). '70' indicates 70 ksi (490 MPa / 70,000 psi), matching ASTM A36, A572 Gr.50, and Q355 structural steels. E60 denotes 60 ksi (415 MPa) for mild carbon steels. Codes mandate matching filler strength to base metal without excessive over-matching that induces cold cracking.
Why should weld leg size be sized within upper and lower limits relative to plate thickness?
A leg size too small on thick plate (e.g. 3mm weld on 20mm plate) suffers severe quenching from rapid base metal heat sink, forming brittle martensite prone to cold cracking. AWS D1.1 mandates minimum weld sizes per plate thickness. Conversely, welds larger than necessary cause excessive angular distortion, residual tensile stress, and wasted labor and filler metal.