Wire Rope Safe Working Load (SWL) Chart

SWL = Minimum Breaking Force ÷ 5

The SWL-to-MBF ratio shall be verified by the manufacturer of the rigging elements; their published rating governs.

Wire Rope, Independent Wire Rope Core (IWRC)

SWL = Minimum Breaking Force ÷ 5

Ratio to be verified by the manufacturer of the rigging elements.

Independent Wire Rope Core; higher strength, crush resistance, and stiffness

Diameter(in)	Weight(lb/ft)	IPS SWL(lbf)	IPS SWL(t)	EIPS SWL(lbf)	EIPS SWL(t)	EEIPS SWL(lbf)	EEIPS SWL(t)
1/4" Suppliers	0.12	1,176	0.53	1,360	0.62	—	—
5/16" Suppliers	0.18	1,832	0.83	2,108	0.96	—	—
3/8" Suppliers	0.26	2,624	1.19	3,020	1.37	3,320	1.51
7/16" Suppliers	0.35	3,556	1.61	4,080	1.85	4,480	2.03
1/2" Suppliers	0.46	4,600	2.09	5,320	2.41	5,840	2.65
9/16" Suppliers	0.58	5,800	2.63	6,720	3.05	7,400	3.36
5/8" Suppliers	0.72	7,080	3.21	8,240	3.74	9,080	4.12
3/4" Suppliers	1.04	10,240	4.64	11,760	5.33	12,960	5.88
7/8" Suppliers	1.41	13,840	6.28	15,920	7.22	17,520	7.95
1" Suppliers	1.85	17,960	8.15	20,680	9.38	22,760	10.3
1-1/8" Suppliers	2.34	22,600	10.3	26,000	11.8	28,600	13.0
1-1/4" Suppliers	2.89	27,760	12.6	31,960	14.5	35,160	15.9
1-3/8" Suppliers	3.49	33,400	15.2	38,400	17.4	42,400	19.2
1-1/2" Suppliers	4.16	39,560	17.9	45,600	20.7	50,000	22.7
1-5/8" Suppliers	4.88	46,000	20.9	52,800	23.9	58,400	26.5
1-3/4" Suppliers	5.66	53,200	24.1	61,200	27.8	67,600	30.7
1-7/8" Suppliers	6.49	60,800	27.6	69,600	31.6	76,800	34.8
2" Suppliers	7.39	68,800	31.2	79,200	35.9	86,800	39.4
2-1/8" Suppliers	8.34	76,800	34.8	88,400	40.1	97,200	44.1
2-1/4" Suppliers	9.35	86,000	39.0	98,800	44.8	108,800	49.4
2-3/8" Suppliers	10.4	95,600	43.4	109,600	49.7	120,400	54.6
2-1/2" Suppliers	11.6	104,800	47.5	120,800	54.8	132,800	60.2
2-5/8" Suppliers	12.8	115,200	52.3	132,400	60.1	145,600	66.0
2-3/4" Suppliers	14	125,600	57.0	144,400	65.5	158,800	72.0
2-7/8" Suppliers	15.3	136,400	61.9	156,800	71.1	172,400	78.2
3" Suppliers	16.6	148,000	67.1	170,000	77.1	187,200	84.9
3-1/8" Suppliers	18	159,600	72.4	183,200	83.1	201,600	91.4
3-1/4" Suppliers	19.5	171,600	77.8	196,800	89.3	216,400	98.2
3-3/8" Suppliers	21	183,600	83.3	211,600	96.0	232,800	105.6
3-1/2" Suppliers	22.7	196,400	89.1	225,600	102.3	248,000	112.5

Pick core and grade from the rope tag or cert first, then read across to the diameter: 3/4 in runs from 47,600 lbf MBF (FC IPS) to 64,800 lbf MBF (IWRC EEIPS), a 36% spread, so never size by diameter alone. A dash means not produced in that grade.

Metric ton (t) columns are derived at 2,204.62 lb/t, to two decimals below 10 t and one above. Display only; the data carries lbf.

Suppliers opens NETWORK filtered to suppliers with known stock at that diameter. Stock ranges are a procurement aid, not confirmed inventory. Verify construction, grade and availability with the supplier.

IPS, Improved Plow Steel

EIPS, Extra Improved Plow Steel

EEIPS, Extra Extra Improved Plow Steel

IPS, Improved Plow Steel · EIPS, Extra Improved Plow Steel · EEIPS, Extra Extra Improved Plow Steel

Tool NotesWhat it does, the formula, and what it assumes

What this tool does

A lookup table of 6×19 wire rope: minimum breaking force and safe working load by diameter, for fiber core and IWRC, in Improved Plow Steel (IPS), Extra Improved Plow Steel (EIPS) and Extra Extra Improved Plow Steel (EEIPS) grades.

Shackle capacities sit alongside it, so the rope and the hardware that terminates it can be picked off the same page.

Formula

Safe working load is minimum breaking force divided by the design factor. The tables here use 5:1, the design factor for wire rope slings.

SWL = Minimum Breaking Force / 5design factor 5:1

Select rope: SWL ≥ required tension

Select shackle: SWL ≥ required tension

Vertical capacity per leg = SWL × sin αα measured from horizontal; an angled leg lifts less than its straight-pull SWL, and the shallower the angle, the less it lifts

Assumptions

The tables list Safe Working Loads (SWL) for wire rope using a 5:1 design factor. Shackles list the manufacturer's stamped Working Load Limit. Values assume a straight vertical pull; no sling-angle reduction, dynamic amplification, or D/d bending loss is built in.

Design factor 5:1, SWL = minimum breaking force ÷ 5. The SWL-to-MBF ratio shall be verified by the manufacturer of the rigging elements; their published rating governs.
Vertical pull, a single leg loaded straight down; angled or multi-leg lifts raise tension and must be derated.
Static, no shock, swing, or impact factor is included.
Condition, a published SWL applies to rope in as-new condition.
Rope SWL, not sling WLL, termination efficiency is not applied. The fabricator's tagged WLL governs for a finished sling.

Technical NotesDerivation, worked example, applications and checks

How values are derived

Rope SWL is the catalog breaking force divided by the design factor; selection returns the smallest size whose SWL meets the required tension. Shackles are chosen by their rated SWL. Minimum breaking force is a published property of the rope; it is never calculated. The equations are in the Formula block above.

Cross-section of 6x19 wire rope: six 19-wire strands laid around an independent wire rope core — 6×19 IWRC in section: six 19-wire strands laid around a core that is itself a small wire rope. Swap that core for fiber and the same diameter is FC, the lighter and weaker half of the table.

Screw pin anchor shackle with 3/4 in and WLL 4 3/4 T stamped on the bow — A 3/4 in shackle is stamped WLL 4-3/4 t (10,472 lb). That figure is read off the bow, not worked out from the rope beside it.

Grades & core, breaking strength IPS < EIPS < EEIPS; an IWRC core is stronger than fiber core (FC).
Shackles are not derived, a shackle carries the manufacturer's stamped Working Load Limit, and the ultimate column is their published minimum, carried as published. The 5:1 design factor is not applied to it in either direction.

Worked example

3/4 in 6x19 IWRC, EIPS grade

Given

Diameter: 3/4 in
Construction: 6×19 IWRC
Grade: EIPS (Extra Improved Plow Steel)

Solve

Minimum breaking force = 58,800 lbffrom the table

SWL = 58,800 / 5 = 11,760 lbfdesign factor 5:1

2-leg pick at 60°: 11,760 × sin 60° × 2 = 20,369 lbusable vertical

Shackle: 3/4 in WLL 10,472 lb < 11,760 lb → use 7/8 in, WLL 14,330 lbfrom the shackle table

11,760 lb per leg vertical. Two legs at 60° will lift roughly 20,370 lb. Same pair at 30°: 11,760 × sin 30° × 2 = 11,760 lb. Sling angle halves the usable lift.

D/d ratio

D/d = D / d. D = diameter of the surface the rope bends around (pin, hook, sheave). d = nominal rope diameter. Larger D/d, gentler bend. Smaller D/d, more bending stress on the wires and less rope efficiency.

3/4 in 6×19 eye-and-eye sling, no thimble

Given

Sling: 3/4 in 6×19 eye-and-eye, no thimble
Connection: the eye goes over a 3/4 in shackle pin, ≈ 0.88 in

Solve

D/d = 0.88 / 0.75 = 1.17

Published sling ratings are commonly based on 25:1

The shackle WLL checks out. The sling does not keep its published capacity at D/d = 1.17. Separate ratings; the connection geometry controls.

No generic reduction factor, efficiency at small D/d depends on construction, grade, termination, and contact geometry. Use manufacturer data or a qualified person, not MBF × a guessed factor. The curve above is illustrative only, not design data.
Thimbles change the connection, a properly sized thimble gives the eye a larger, controlled bearing surface. Consider a thimble where the eye connects directly to shackles, hooks, or master links, especially on repeat use.
Unthimbled eye-and-eye slings, are made for basket and choker hitches, where the sling body wraps the load. In a vertical hitch, keep the bare eye off small pins.
Fixes, larger-radius pin, hook or sheave; a thimble; a manufacturer-rated sling/shackle pairing; or a rated synthetic sling where the geometry forces a small radius.

Sling hitches and sling types

Vertical, choker and basket hitches shown side by side with capacity factors of 1.0, 0.8 and 2.0 — Vertical, choker and basket, with the factor each applies to the sling's rated vertical capacity.

Sling hitch types & capacity

Factors are relative to the sling's rated vertical capacity.

Hitch	Typical factor	Description
Vertical	1.00×	One vertical leg supports the load.
Basket	2.00×	Two portions of the sling carry the load.
Choker	0.75–0.80×	Sling passed around the load and choked.

Basket and choker factors are typical values, not universal ratings. Factors assume vertical legs; angled rigging reduces capacity further. Manufacturer's published rating for the specific configuration governs.

Synthetic vs wire rope slings

Synthetic (round and flat/web) slings are light, flexible, easy to handle, and kind to finished surfaces; round slings conform best, web slings position easily. Wire rope is heavier and stiffer but stands up to abrasion, rough handling, and heat, so it carries most heavy construction picks.

	Synthetic	Wire rope
Weight	Light	Heavy
Flexibility	Excellent	Moderate
Surface protection	Excellent	Lower
Abrasion / cut resistance	Lower	Higher
Heat resistance	Lower	Higher
Best suited for	Finished, irregular, lighter loads	Heavy, rough, abrasive work

Synthetics cut, abrade, and heat-damage easily: protect every edge. Wire rope can mark load surfaces and needs inspection for broken wires, kinks, bird-caging, and corrosion.

Applications & rules of thumb

Mind the D/d ratio, bending rope over a small pin or sharp edge cuts its strength; keep the bend diameter large. The D/d ratio group above is where the numbers and the fixes are.
Derate for dynamics, fast picks, swinging, or unequal legs push real tension above the static value; add margin.
Pair with Pick Points, use the Pick Points tool to get the actual leg tension and angle, then size rope and shackle here.

Field notes

5:1 is the typical factor for wire rope slings. It is not universal, as some owners and jurisdictions specify higher. Confirm before you use these numbers.
All rigging shall be inspected periodically, before and after use. Any rigging with broken wires, kinks, bird-caging, crushing or corrosion shall be removed from service immediately.
Terminations govern. A wire rope clip assembly develops roughly 80% of the rope's strength; a properly poured or swaged socket develops close to 100%.
Extra caution with synthetics, more open to cuts, abrasion, UV, heat, and chemicals than wire rope. Pad every edge; inspect before use.

Educational reference only. Verify every result independently and apply the safety factors and load combinations required by the governing code and a qualified engineer.

Quick reference

QR01 - Sling Tension
PDF · 579 KB — Static Pick Analysis - Sling Tension and Angle 2 vs. 4-Sling Comparison, Equations, Worked Examples, Field Notes + More
QR02 - Rigging
PDF · 1.0 MB — Wire Rope SWL - Selection, D/d Ratio, Sling Hitches, MBF Tables Equations, Worked Examples, Diagrams, Field Notes, Wire Rope and Shackle MBF Tables + More

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