Chain Grades Explained — Grade 30, 43, 70, 80, 100 and 120
The grade number on a chain or a chain fitting is not a model number and not a brand. It is the strength of the steel, written as a number. Once you can read it, most of the confusing markings on lifting hardware stop being confusing.
What the number means
The grade is the nominal breaking stress of the steel in newtons per square millimetre, divided by ten. Grade 80 steel reaches a mean stress of 800 N/mm² across the two link sections at minimum breaking load. Grade 100 reaches 1 000 N/mm². Grade 30 reaches 300.
That is the whole rule, and it explains the arithmetic everyone quotes: Grade 100 is 1000/800, so about 25% more load than Grade 80 at the same size; Grade 120 is 1200/800, so about 50% more. Same link, same diameter, better steel.
The working load limit is a different number again — the breaking load divided by a design factor, commonly 4:1 for Grade 80 and Grade 100 chain slings. The factor belongs to the standard the sling is built to, so read it off the certificate rather than assuming it.
The ladder
| Grade | Also called | Nominal breaking stress | Steel | What it is for | Overhead lifting? |
|---|---|---|---|---|---|
|
Grade 30 G30 |
Proof Coil | 300 N/mm² | Low carbon steel | General utility, guard chain, barriers, farm and yard work | No |
|
Grade 43 G43 |
High Test | 430 N/mm² | Carbon steel | Logging, agriculture, towing, general load securement | No |
|
Grade 70 G70 |
Transport / binder chain | 700 N/mm² | Heat treated carbon steel | Load securement and tie-down on trucks and trailers. The yellow chromate chain | No |
|
Grade 80 G80 |
Alloy — the first lifting grade | 800 N/mm² | Quenched and tempered alloy steel | Chain slings and overhead lifting, when certified | Yes, certified |
|
Grade 100 G100 |
Alloy | 1000 N/mm² | Quenched and tempered alloy steel | Chain slings and overhead lifting, when certified. About 25% more load than Grade 80 at the same size | Yes, certified |
|
Grade 120 G120 |
Alloy | 1200 N/mm² | Quenched and tempered alloy steel | Chain slings and overhead lifting, when certified. About 50% more load than Grade 80 at the same size | Yes, certified |
Grade 30, 43 and 70 are carbon-steel chains. They are strong, and they are not lifting chain: they are not made, tested or certified for loads suspended over people. Grade 80 and above are quenched and tempered alloy, which is what makes them suitable — provided they are certified.
Reading the marks on a fitting
Connecting links, hooks and master links are marked size then grade, which looks like a part number and is not one:
- 6-8 — fits 6 mm chain, Grade 8. The trailing digit is the grade.
- 18/20-8 — one fitting covering both 18 mm and 20 mm chain, Grade 8.
- 7/8-10 — fits 7 mm and 8 mm chain, Grade 10. In North American sizing ¼″ alloy chain is 7 mm nominal and ⁵⁄₁₆″ is 8 mm, so one fitting covers both trade sizes.
- G-80 / G-100 — the grade again, in North American style. Europe writes the same thing as 8 and 10.
So Grade 10 and Grade 100 are the same grade, and neither is a manufacturer's name. Two numbering conventions, one steel.
The standards
Chain and the fittings that join it are covered by different standards, which is worth knowing when a supplier quotes only one of them.
| Standard | Covers |
|---|---|
| EN 818-2 | Short link chain for lifting, Grade 8 — the chain itself |
| EN 818-4 | Chain slings, Grade 8 — the assembly |
| EN 1677-1 | Components for slings — forged steel components, Grade 8 |
| EN 1677-4 | Components for slings — links, Grade 8. Master links, intermediate links and terminal links, 0.25 t to 132 t |
| ASTM A391/A391M | Grade 80 alloy steel chain |
| ASTM A973/A973M | Grade 100 alloy steel chain |
| ASTM A952/A952M | Forged Grade 80 and Grade 100 lifting components and welded attachment links |
| ISO 1834 | Short-link chain for lifting — general conditions of acceptance |
| DIN 5687-3, DIN 5688-3 | The older German numbering — Grade 8 round steel chain, and Grade 8 chain slings and their terminal fittings. Where the size-grade marking convention comes from |
| ASME B30.9, ASME B30.26, OSHA 1910.184 | North American rules for using slings and rigging hardware, rather than for making them |
The mark is not the certificate
This is the part that costs people money.
Under EN 1677-4 and ASTM A952, proof testing and traceability are part of what a Grade 80 component is. A forged “8” on a link tells you what the maker intended. A test certificate tells you the link in your hand was actually made and proved to the standard, by a maker you can trace.
Unmarked and uncertified imports are stamped with grades all the time. If there is no certificate, the honest description is general-purpose hardware — whatever the stamp says, and however good the link may turn out to be. Do not use it for overhead lifting, and never for anything holding a person.
Our own connecting links are a hardware item and carry no certificates. We say so on the product page rather than in the small print, and we do not sell them for overhead lifting.
Marine chain is a different system
None of the above applies to anchor and mooring chain. Marine stud link chain is graded U1, U2 and U3 under IACS rules and certified by a classification society — Lloyd's Register, ABS or DNV. A Grade 80 number and a U3 number are not comparable and the fittings are not interchangeable. See the anchor chain grades guide for that ladder.
In short
- The grade is the steel's breaking stress in N/mm², divided by ten.
- Grade 10 and Grade 100 are the same thing. So are Grade 8 and Grade 80.
- Grade 30, 43 and 70 are not lifting chain, whatever they are used for.
- Grade 80 and above are lifting grades when certified. The mark is not the certificate.
- Marine U1/U2/U3 is a separate system — do not mix them.
Send us the marking off a fitting you already have and we will tell you the size and the grade — ask us, or start with the Grade 80 and Grade 100 chain connectors, 6 mm to 32 mm.