Lifting Lug calculator
Check a pad eye against sling angle, dynamic factor and every plate failure mode bearing, tear-out, net section, gross section and the weld group. Results come with a scaled detail, and a calculation note you can print.
Engineering tools · Lifting & rigging
Run the check
Enter the load, geometry and material. The tool resolves sling forces, applies your dynamic factor, and reports a utilisation for every failure mode.
What it actually checks
Six checks run on every lug: tensile rupture on the net area through the pin hole, double-plane shear from the hole to the free edge, bearing on the projected pin contact area, the Whitmore section through the lug body in tension and compression, the fillet weld to the base, and the pin-to-hole fit limit that keeps bearing spread over the contact face.
The three inputs people get wrong
Sling angle is the big one at 45° from vertical the lug sees about 1.41 times the vertical share, and at 60° it sees 2.0. Riggers shorten slings on site to clear obstructions and quietly double the design force. Second is the design category: the lower one assumes an engineered lift with a known weight, and the higher one covers everything else. Third is pin diameter use the shackle you will actually rig with, not a nominal size, because the clearance drives bearing and tear-out.
What it does not cover
The receiving member. A lug can pass every check while the flange it is welded to yields locally or the web crumples and that is where most real failures start. Also outside scope: out-of-plane loading when the crane drifts, fatigue on lugs that are lifted repeatedly, and lamellar tearing in thick plate loaded through the thickness.
Common questions
Answered below design category selection, why sling angle matters so much, when cheek plates help and when they do nothing, and whether the output can go into a submittal.
What is the difference between AISC 360 and ASME BTH-1 for a lifting lug?
AISC 360 gives you the strength equations how a plate ruptures at a hole, how a weld resists load. ASME BTH-1 gives you the safety framework: design categories, service classes, and design factors that reflect how well the load is known and how many cycles the lug will see. Designing a lug on building code load factors alone typically produces something under-designed for lifting, because the building code was never written for a suspended dynamic load with people underneath.
Which design category should I use?
The lower category assumes the load magnitude is predictable and the lift is engineered a planned pick with a known weight. The higher category, with its larger design factor, covers loads that are not accurately known or environments that are uncertain. When in doubt take the higher one; the difference is a few millimetres of plate.
Why does the sling angle change the answer so much?
Because the lug sees force along the sling, not vertically. About 1.15× the vertical share at 30° from vertical, 1.41× at 45°, and 2.0× at 60°. Shallow slings are the single most common reason a lug that passed on paper fails on site.
Need the lift plan, not just the lug?
A lug that passes is one line in a lift plan. The package a consultant approves also covers the receiving member, temporary lifting points, centre of gravity and rigging arrangement, crane selection, ground bearing pressure, and stability of the piece in the air. We produce those for steel erection across the Kingdom.
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