Groove / Butt Weld Strength Calculator

CJP and PJP effective throat & design strength

Size complete and partial joint penetration groove welds with effective throat, throat area, nominal strength Rn, and design strength φRn. Optional applied-load pass/fail check. Distinct from fillet weld strength. Companion articles: strength guide, troubleshooting, and joint prep technique.

Also try our Fillet Weld Strength Calculator and Weld Joint Design Calculator.

Under review: CJP tension and compression results are verified (base metal governs per AISC Table J2.5). CJP shear is being re-checked: the base-metal shear yielding and rupture checks of AISC J4 are not applied yet, so the shear result can read high. Check CJP shear against AISC J4.

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Recommended groove welding gear

Wire, machines, and consumables for structural groove and butt welds

MIG wire

Hobart ER70S-6 MIG Wire

Matches E70XX strength class
Clean mild steel groove fills
Common .035 in diameter

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Multi-process

Lincoln Power MIG / Multi-process

Structural light fab capacity
Stable arc for groove root passes
Verify duty cycle for long fills

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Stick

7018 Stick Electrodes

E70XX class for structural steel
Common for CJP / PJP field work
Store dry for low hydrogen

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CJP vs PJP groove welds

CJP (complete joint penetration) develops the full thickness of the plate — effective throat equals plate thickness for a matching butt weld. Strength is often governed by the base metal when filler matches Fy/Fu requirements.

PJP (partial joint penetration) has an effective throat less than plate thickness. Design strength uses Fw = 0.60 × FEXX on the effective throat area Awe = te × L, with φ typically 0.80 (LRFD).

When groove vs fillet

Grooves are preferred for butt joints and thicker members where fillet legs would become huge. Fillets suit T-joints and lap joints. Use the fillet weld strength calculator for equal-leg fillets (throat = 0.707 × leg).

AWS notes

Always follow the WPS, AWS D1.1 prequalified joint details, and inspection criteria. This tool is a planning estimate — not a sealed engineering calculation.

Frequently asked questions

What is effective throat for PJP?

It is the minimum distance from the root of the joint to the face of the weld, minus any incomplete fusion allowance required by code. Enter the design effective throat from the detail.

Groove / Butt Weld Strength Calculator