Weld Strength Calculator

Work out weld strength instantly with clear inputs, formula shown and shareable results.

About Weld Strength Calculator

Fillet weld capacity is the effective throat area multiplied by the allowable shear stress, conventionally 0.30 times the electrode tensile strength. Throat area is 0.707 times leg size times effective length, so capacity is directly proportional to leg size, not to its square.

Formulas

Throat area

A = 0.707 x leg x effective length

Capacity

Capacity = A x 0.30 x electrode tensile strength

Worked example

With the default values below, Weld Strength Calculator returns Weld design capacity of 78.26. Change any input above and every figure here is recalculated in your browser.

Inputs used

Fillet leg sizeminimum 1 mm: 6 mm
Effective weld lengthminimum 5 mm: 150 mm
Electrode tensile strengthminimum 100 MPa: 410 MPa

Results

Weld design capacity: 78.26 kN
Effective throat area: 636.3 mm²
Allowable shear stress: 123.0 MPa
Capacity in tonnes force: 7.98 t

Step by step

1Values used
2Throat area
3Capacity
4Weld design capacity= 78.26 kN
5Effective throat area= 636.3 mm²
6Allowable shear stress= 123.0 MPa
7Capacity in tonnes force= 7.98 t

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Weld capacity must be verified against the governing structural welding code, including electrode matching and inspection requirements.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Weld capacity must be verified against the governing structural welding code, including electrode matching and inspection requirements.

Frequently Asked Questions

How is the Weld Strength figure worked out?

A = 0.707 x leg x effective length. Fillet weld capacity is the effective throat area multiplied by the allowable shear stress, conventionally 0.30 times the electrode tensile strength.

Does weld direction change capacity?

Some codes allow a higher stress for welds loaded transversely than longitudinally. The 0.30 factor used here is the conservative direction-independent value.

What values do I need to enter?

This calculator takes 3 inputs: Fillet leg size, Effective weld length, Electrode tensile strength. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.