How this calculator works
A right-angle equal-leg fillet has theoretical throat equal to leg size divided by sqrt(2). Effective throat area is throat times effective line length. All fillet directions use the same supplied throat stress with no directional strength increase. Butt throats must be qualified effective penetration; two throats are added only when they represent non-overlapping effective areas. This average-stress model excludes eccentric weld groups, fatigue and base-metal failure.
Formula
Fillet throat a=s/sqrt(2); A=a x total effective length; nominal F=A x supplied throat stress. Two equal lines use total length=2L; combined layout uses Ltransverse+2Lparallel. Butt A=(a1+a2)L where applicable.
Worked example
A single 100 mm effective fillet with 6 mm legs has a 4.24264 mm throat and 424.264 mm^2 area. At a supplied 100 MPa throat stress its nominal load is 42.4264 kN.
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Frequently asked questions
Is the entered stress electrode tensile strength?
No. Enter the applicable design or allowable throat stress after required factors. The page does not derive it from electrode classification.
Can I sum two butt penetration depths?
Only if the effective regions do not overlap. Never count the same material twice.
Does this design a structural connection?
No. Results are estimates and are not a substitute for a licensed engineer. Bearing, connections, stability, local code requirements and all applicable load combinations need separate checks.