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Two-leg anchor load calculator

This page reports what the official source says. It is not legal advice: ask the office named here. Type a load and the angle between the two legs of an anchor to see the load on each leg when the legs are the same length. OSHA, whose rigging rule for material handling is cited here, is the office named here.

Checked against the sources at the bottom of this page on October 8, 2026. Published tables are revised: the source has the last word.

Work it out

How the answer is worked out

Load on each leg = the load divided by 2 times the cosine of half the angle between the legs. The two legs are taken as the same length, so they carry the same share.

Each leg's angle from horizontal = 90 degrees minus half the angle between the legs, and the same sum can be written as the load divided by 2 times the sine of that angle from horizontal.

The load is changed to newtons first. 1 kilogram-force is 9.80665 newtons and 1 pound-force is 4.4482216152605 newtons, as NIST prints them.

What the sources say

OpenStax College Physics, from Rice University, works a tightrope example: a wire sags 5.0 degrees under a 70.0 kg walker. The horizontal parts of the two tensions cancel, the vertical parts together equal the weight, and the tension is the weight divided by 2 times the sine of the angle from horizontal. The book gets 3900 N and says that is almost six times the walker's 686 N weight, because the wire is nearly horizontal.

The book's section 4.7, Further Applications of Newton's Laws, adds a traffic light hung from two wires at different angles. It says the two tensions are equal if and only if the angles on either side are the same, and that both tensions grow when both wires are more horizontal. The calculator on this page covers the equal-angle case only.

OSHA's rule on rigging equipment for material handling, 29 CFR 1926.251, says wire rope slings carry markings that state the size, the rated capacity for each type of hitch, the angle on which that rating is based and the number of legs if more than one. It words the same marking duty for fiber rope slings.

The page checks no rating. The load on a leg is arithmetic on typed numbers, and nothing on it says what a sling, ring, rope or anchor point is rated for.

Arithmetic only. The answer is only as good as the numbers entered. It is not a plan or a safe working load for any job.

Sources