Fillet Weld Calculator — Simplified Method

Fillet weld assessment per EN 1993-1-8 (EC3), simplified method

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Load Type

mm
Effective throat of fillet weld
mm
Effective length (each weld)
Symmetric welds in joint
kN
Design value (factored)
EN 1993-1-8 §2.2

Results

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Enter values
Weld throat area Aw
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Applied stress σw
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Design resistance fw,Rd
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Utilisation η
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Resistance force FRd
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Reserve capacity
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Weld geometry invalid: effective length must be ≥ 6a and ≥ 30 mm (EC3 §4.5.1).
Throat thickness a < 3 mm — minimum recommended for structural welds.
Utilisation > 80% — consider increasing throat thickness or weld length.
Effective length used: leff = l − 2a (start/stop deduction per EC3 §4.5.1).

Diagram

Method — EC3 Simplified

Design resistance

Per ČSN EN 1993-1-8 §4.5.3.3 (simplified method), the design shear strength of the weld throat is:

fvw,d = (fu / √3) / (βw · γM2)

Resistance per unit length: Fw,Rd = fvw,d · a. The weld is adequate when the resultant force per unit length on the throat stays below Fw,Rd — the simplified method does not resolve the load into separate normal/shear components.

Correlation factor βw & notes

  • S235 — βw = 0.80, fu = 360 MPa
  • S275 — βw = 0.85, fu = 430 MPa
  • S355 — βw = 0.90, fu = 490 MPa
  • S460 — βw = 1.00, fu = 540 MPa

γM2 = 1.25 (standard) per EN 1993-1-8 §2.2. Effective length leff = l − 2a removes the start/stop craters (§4.5.1); keep leff ≥ max(6a, 30 mm).