Pick point load share: how much each lift point carries

How to use the pick point calculator

1. Enter the load weight in lb or kg. If you came from the load weight calculator, it is filled in for you.
2. Pick a distance unit, then enter either the positions of A, B and the CG measured from the same end of the load, or the span from A to B and the CG's distance from A.
3. Optionally enter the hook height above the pick points to see each sling's angle and tension. The tool assumes one hook directly above the CG, with slings to two pick points level with each other, so the hook height sets both angles.
4. Read the share at each point and the steps under it. If the CG is on or outside a pick point, the calculator says so instead of giving a share.

How the load share works

A level load hanging from two points is balanced when the turning effect of its weight about each point is matched by the other point. That is moment balance, the same statics as a beam on two supports. Call the CG's distance to A a and to B b:

• Share at A = W × b ÷ (a + b).
• Share at B = W × a ÷ (a + b).
• The shares add up to W. The point closer to the CG carries more, and a CG at the midpoint gives 50% each.
• Sling tension = share ÷ sin(angle), with the angle from horizontal. The model is one hook directly above the CG, with slings to two pick points level with each other, so the angles are set by the hook height h: angle at A = atan(h ÷ a) and angle at B = atan(h ÷ b). The tension comes straight from the sling angle calculator, and the tool uses the same lower limit of 5°, so a hook too low for the rig gives an error instead of tensions.
• With the angles set this way, both slings pull sideways by the same amount (share ÷ tan(angle)), so the hook balances. The calculator shows that pull as a check.

The derivation follows OpenStax, Conditions for Static Equilibrium, and the U.S. Department of Energy, Hoisting and Rigging Fundamentals covers the CG and sling loading in rigging terms. Conversions use 1 lb = 0.45359237 kg from NIST.

To check a share against what a sling can hold for its hitch, the sling capacity calculator works from the tagged rating. For what the CG is and how it is found, read center of gravity of a load.

Worked example 1: CG at the midpoint

Invented numbers. An 8,000 lb load with pick point A at 2 ft, pick point B at 22 ft and the CG at 12 ft, all measured from the left end. The CG is a = 12 − 2 = 10 ft from A and b = 22 − 12 = 10 ft from B, a span of 20 ft. Share at A = 8,000 × 10 ÷ 20 = 4,000 lb. Share at B = 8,000 × 10 ÷ 20 = 4,000 lb. That is 50% each, and 4,000 + 4,000 = 8,000 lb.

Worked example 2: off-center CG with a hook height

Invented numbers. A 12,000 lb load with a 16 ft span and the CG 4 ft from A, so a = 4 ft and b = 16 − 4 = 12 ft. Share at A = 12,000 × 12 ÷ 16 = 9,000 lb (75%). Share at B = 12,000 × 4 ÷ 16 = 3,000 lb (25%).

One hook sits directly above the CG, with slings to A and B, which are level with each other. The hook is 4√3 ≈ 6.93 ft above the pick points, so the angle at A = atan(6.93 ÷ 4) = 60° and the angle at B = atan(6.93 ÷ 12) = 30° from horizontal. The sling to the nearer point A is steeper. Tension at A = 9,000 ÷ sin 60° = 9,000 ÷ 0.866025 = 10,392.3 lbf. Tension at B = 3,000 ÷ sin 30° = 3,000 ÷ 0.5 = 6,000 lbf. Check: each sling pulls 9,000 ÷ tan 60° = 3,000 ÷ tan 30° = 5,196.15 lbf sideways, so the hook balances. The sling at A carries the larger share, and the low angle at B doubles its share into tension.

These are original arithmetic examples, not exam questions.

Common mistakes

• Swapping the distances. A carries W × b, the distance to the other point. Giving the nearer point the smaller share is the most common slip; the nearer point always carries more.
• Assuming an even split. Two pick points share 50/50 only when the CG is exactly midway between them.
• Mixing datums. Measure A, B and the CG from the same end of the load, in the same unit.
• Using the share as the sling load. An angled sling carries more than its share: tension = share ÷ sin(angle).
• Picking angles that do not match the rig. With one hook above the CG, the angles follow from the hook height and the distances, which is why this tool asks for the height and not the angles. The unequal-legs mode of the sling angle calculator works the same geometry.
• Leaving out the rigging. Weigh in anything that hangs below the pick points and moves with the load.

Pick point load share questions

Working out how a load splits between pick points is the kind of rigging arithmetic the NCCCO written exams ask about. This tool shows the arithmetic and does not approve a lift.