What is the breaking strength of 12 mm wire rope?

For 6x19 line-contact rope in 1770 grade, 84.1 kN with a fibre core and 90.7 kN (about 9.24 t) with a steel core. Our compacted 6x19S steel-core rope breaks at 11.3 t at 12 mm.

What is the breaking strength of 16 mm wire rope?

For 6x19 line-contact rope in 1770 grade, 150 kN fibre core and 161 kN steel core. In 6x36WS, 150 kN and 161 kN.

How do I convert wire rope breaking strength from kN to tonnes?

Divide by 9.81. 161 kN is about 16.4 t.

What is the safe working load of wire rope?

For a sling: the minimum breaking load × the termination efficiency ÷ the design factor, which is 5 for general lifting. The maker calculates it and marks it on the sling. For a hoist rope, the design factor depends on the machine.

Is IWRC wire rope stronger than fibre core?

Yes, by about 8% at the same diameter and grade, and it resists crushing on a drum. A fibre core is more flexible.

Rigging capacity charts

Wire rope breaking strength chart: minimum breaking load by diameter, construction and grade

Minimum breaking loads for steel wire rope from 5 mm to 60 mm in 6x19 line-contact, 6x36WS and compacted constructions, by tensile grade and core, in kN and tonnes — with a construction-by-construction comparison, weights, and how a breaking load becomes a working load.

Written by: Ayush Bhatia, Director
Published: 13 October 2026
Reading: 8 min · 5 sections
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At a glance

Key takeaways

A 12 mm 6x19 line-contact rope in 1770 grade breaks at no less than 84.1 kN with a fibre core and 90.7 kN with a steel core (IWRC).
A steel core adds about 8%; going from 1770 to 1960 grade adds about 11%. The common six-strand constructions sit within about 12% of each other at the same diameter.
Compacted rope packs more steel into the diameter and breaks highest of all at a given size.
Breaking strength is not working load. A sling is rated at MBL × termination efficiency ÷ 5; hoist ropes use the machine’s own design factor.
Divide kN by 9.81 for tonnes. Every figure here is a minimum breaking load for new rope.

Figures verified 13 October 2026 · Minimum breaking loads and weights from our wire rope listings; conversions ours, rounded down. Termination efficiencies from the EN 13411 series. The rope certificate governs.

The breaking strength of a wire rope is set by three choices: its diameter, the tensile grade of its wires and its core. Construction — 6x19, 6x36, compacted — changes how it handles more than how strong it is. The charts below give the minimum breaking load for the ropes we list, by all three, so you can read off the rope and then work down to a safe load.

/016x19 line-contact rope (6x19S and 6x19W).

The general-purpose rope class for slings and rigging. Minimum breaking load in kN by tensile grade and core, with the 1770 IWRC figure in tonnes.

6x19S / 6x19W wire rope — minimum breaking load (kN), from our table

Rope	1770 FC	1770 IWRC	1960 FC	1960 IWRC	1770 IWRC (t)	Weight IWRC (kg/100 m)
5 mm	14.6	15.8	16.2	17.4	1.61	10.1
6 mm	21	22.7	23.3	25.1	2.31	14.6
7 mm	28.6	30.9	31.7	34.2	3.15	19.9
8 mm	37.4	40.3	41.4	44.7	4.1	25.9
9 mm	47.3	51	52.4	56.5	5.2	32.8
10 mm	58.4	63	64.7	69.8	6.42	40.5
11 mm	70.7	76.2	78.3	84.4	7.77	49.1
12 mm	84.1	90.7	93.1	101	9.24	58.4
13 mm	98.7	107	109	118	10.9	68.5
14 mm	115	124	127	137	12.6	79.5
15 mm	131	142	146	157	14.4	91.2
16 mm	150	161	166	179	16.4	104
18 mm	189	204	210	226	20.8	131
19 mm	211	228	234	252	23.2	146
20 mm	234	252	259	279	25.6	162
22 mm	283	305	313	338	31.1	196
24 mm	336	363	373	402	37	234
26 mm	395	426	437	472	43.4	274
28 mm	458	494	507	547	50.3	318
30 mm	526	567	582	628	57.8	365
32 mm	598	645	662	715	65.7	415
34 mm	675	728	748	807	74.2	469
36 mm	757	817	838	904	83.3	526
38 mm	843	910	934	1,010	92.7	586
40 mm	935	1,010	1,030	1,120	102.9	649
42 mm	1,030	1,110	1,140	1,230	113.1	715
44 mm	1,130	1,220	1,250	1,350	124.4	785
46 mm	1,240	1,330	1,370	1,480	135.6	858
48 mm	1,350	1,450	1,490	1,610	147.8	934
50 mm	1,460	1,580	1,620	1,740	161.1	1,010
52 mm	1,580	1,700	1,750	1,890	173.3	1,100
54 mm	1,700	1,840	1,890	2,030	187.6	1,180
56 mm	1,830	1,980	2,030	2,190	201.9	1,270
58 mm	1,960	2,120	2,180	2,350	216.1	1,360
60 mm	2,100	2,270	2,330	2,510	231.4	1,460

Our 6x19S / 6x19W listing runs to 80 mm; the chart stops at 60 mm, where most rigging work ends. Larger sizes are on the product page.

/026x36WS rope.

Warrington-Seale is the usual construction for crane ropes, hoists and flexible slings — more wires per strand, so it bends more easily and lasts longer over sheaves.

6x36WS wire rope — minimum breaking load (kN) and weight, from our table

Rope	1570 FC	1770 FC	1570 IWRC	1770 IWRC	Weight FC (kg/100 m)	Weight IWRC (kg/100 m)
8 mm	33.2	37.4	35.8	40.3	24.3	26.8
10 mm	51.8	58.4	55.9	63	38	41.8
12 mm	74.6	84.1	80.5	90.7	54.7	60.2
13 mm	87.6	98.7	94.5	106	64.2	70.6
14 mm	102	114	110	124	74.5	81.9
16 mm	133	150	143	161	97.3	107
18 mm	168	189	181	204	123	135
20 mm	207	234	224	252	152	167
22 mm	251	283	271	305	184	202
24 mm	298	336	322	363	219	241
26 mm	350	395	378	426	257	283
28 mm	406	458	438	494	298	328
30 mm	466	526	503	567	342	376
32 mm	531	598	572	645	389	428
34 mm	599	675	646	728	439	483
36 mm	671	757	724	817	492	542
38 mm	748	843	807	910	549	604
40 mm	829	—	894	—	608	669
42 mm	914	—	986	—	670	737

/03Construction by construction.

At the same diameter, grade and core, the common six-strand constructions break within about 12% of each other; compacted rope stands clear of them. All figures 1770 grade with a steel core (IWRC), in kN:

Minimum breaking load (kN) by construction at 1770 IWRC, from our tables

Rope	6x7	6x19 (point)	6x19S/W (line)	6x36WS	6x37 (point)	Compacted 6x19S
8 mm	40.7	37.6	40.3	40.3	36.1	—
10 mm	63.5	58.8	63	63	56.5	—
12 mm	91.5	84.6	90.7	90.7	81.3	110
14 mm	125	115	124	124	111	150
16 mm	163	150	161	161	145	196
18 mm	206	190	204	204	183	248
20 mm	254	235	252	252	226	306
22 mm	308	284	305	305	273	370
24 mm	366	339	363	363	325	441
26 mm	430	397	426	426	382	517
28 mm	498	461	494	494	443	601
32 mm	651	602	645	645	578	784
36 mm	824	762	817	817	732	993
40 mm	1,020	940	1,010	—	903	1,225

Compacted figures are converted from tonnes in our table and rounded down. The five standard constructions sit within about 12% of each other; choose construction for how the rope works — abrasion, bending, crushing on a drum — and then size it for the load. Our guide to wire rope construction explains the trade-off.

/04Compacted 6x19S rope.

Compacted strands are drawn through a die before closing, which flattens the outer wires. More steel fits in the diameter and the smooth surface resists wear and crushing. Steel core, in tonnes:

Compacted 6x19S steel-core wire rope — minimum breaking load (t), from our table

Rope	1770	1960	2160	Weight (kg/m)
11.2 mm (7/16″)	9.8	10.6	—	0.57
12 mm	11.3	12.1	—	0.65
12.7 mm (1/2″)	12.6	13.6	—	0.73
13 mm	13.2	14.3	—	0.76
14 mm	15.3	16.5	17.3	0.89
14.3 mm (9/16″)	16	17.2	18	0.92
15 mm	17.6	19	19.8	1.02
16 mm (5/8″)	20	21.6	22.6	1.16
17.5 mm (11/16″)	23.9	25.8	27	1.38
18 mm	25.3	27.3	28.6	1.46
19 mm (3/4″)	28.2	30.4	31.8	1.63
20 mm	31.3	33.7	35.3	1.81
21 mm (13/16″)	34.5	37.2	38.9	1.99
22 mm	37.8	40.8	42.7	2.19
22.2 mm (7/8″)	38.6	41.7	43.5	2.23
24 mm (15/16″)	45	48.6	50.8	2.6
25 mm	48.8	52.7	55.1	2.83
25.4 mm (1″)	50.4	54.4	56.9	2.92
26 mm (1-1/16″)	52.8	57	59.6	3.06
28 mm	61.3	66.1	69.1	3.54
28.6 mm (1-1/8″)	63.9	69	72.1	3.7
30 mm (1-3/16″)	70.3	75.9	79.3	4.07
31.5 mm (1-1/4″)	77.5	83.7	87.5	4.49
32 mm	80	86.4	90.3	4.63
34 mm	90.3	97.5	101.9	5.23
35 mm (1-3/8″)	95.7	103.3	108	5.54
36 mm	101.3	109.3	114.2	5.86
38 mm	112.8	121.8	127.3	6.53
38.1 mm (1-1/2″)	113.4	122.4	127.9	6.56
40 mm	125	134.9	—	7.23
42 mm	137.8	148.8	—	7.97
44 mm	151.3	163.3	—	8.75
44.5 mm (1-3/4″)	154.4	166	—	8.93
46 mm	165.3	178.5	—	9.56
48 mm	180	—	—	10.41
50 mm	195.3	—	—	11.3
50.8 mm (2″)	201.3	—	—	11.66
52 mm	211.3	—	—	12.22

/05From breaking load to working load.

A breaking load is the force that breaks new rope in a tensile test. Nothing is ever lifted on it. For a sling, the working load limit is the rope’s minimum breaking load, multiplied by the efficiency of the eye termination, divided by the design factor:

Design factor: 5 for general-purpose slings under EN 13414. Running ropes on cranes and hoists use the factor set for the machine’s classification, which is usually different.
Termination efficiency: at least 0.9 for ferrule-secured eyes, 0.8 for spliced eyes and 1.0 for poured sockets, under the EN 13411 series.
Illustration: 16 mm 6x36WS, 1770 IWRC, breaks at 161 kN (16.4 t). With a ferrule eye: 161 × 0.9 ÷ 5 = about 2.95 t. That shows the arithmetic only — the rating of a real sling is the one its maker marks on the tag.

Conversions: 1 t = 9.81 kN = 2,205 lb. 1 kN = 225 lbf. The minimum breaking load on a rope certificate is the figure the rope must exceed in test; the actual breaking load measured is usually higher, but a rating is never built on it.

Wire rope in these charts

Common questions

What is the breaking strength of 12 mm wire rope?: For 6x19 line-contact rope in 1770 grade, 84.1 kN with a fibre core and 90.7 kN (about 9.24 t) with a steel core. Our compacted 6x19S steel-core rope breaks at 11.3 t at 12 mm.
What is the breaking strength of 16 mm wire rope?: For 6x19 line-contact rope in 1770 grade, 150 kN fibre core and 161 kN steel core. In 6x36WS, 150 kN and 161 kN.
How do I convert wire rope breaking strength from kN to tonnes?: Divide by 9.81. 161 kN is about 16.4 t.
What is the safe working load of wire rope?: For a sling: the minimum breaking load × the termination efficiency ÷ the design factor, which is 5 for general lifting. The maker calculates it and marks it on the sling. For a hoist rope, the design factor depends on the machine.
Is IWRC wire rope stronger than fibre core?: Yes, by about 8% at the same diameter and grade, and it resists crushing on a drum. A fibre core is more flexible.

ISO 4309ISO

Cranes — Wire ropes — Care and maintenance, inspection and discard

How crane ropes are inspected in service and when they are discarded — broken wires over a stated length, loss of diameter, corrosion and deformation such as kinks, birdcaging and core protrusion. A breaking-strength chart describes new rope; this standard decides when rope in service no longer meets it.

IndustryMarine and offshoreDeck equipment, splash zone and vessel hydraulics.

What next

Replacing a rope?

Send the diameter, construction, grade and core from the old certificate or reel, and the machine it runs on. We will quote matching rope cut to length, with the manufacturer’s certificate.

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