Getting the chain measurement wrong does not just mean ordering the wrong product. On a worksite, an incorrectly sized chain sling poses a safety risk with real consequences.
Selecting a chain that cannot handle the rated load or that does not fit the rigging hardware correctly puts the entire lift at risk.
According to the HSE’s 2024/25 statistics, there were 124 worker fatalities across Great Britain in that period, with struck-by-load and equipment-collapse incidents continuing to feature in the annual figures.
Lifting equipment rarely gives a warning when it fails.
Understanding how to measure chain link size correctly is a basic requirement for anyone specifying or procuring lifting chains in the UK.
This guide covers every measurement that matters, what the figures mean in practice, and how to cross-reference them against a chain link size chart.
Site managers, riggers, and procurement teams who know how to accurately measure chain link size reduce the risk of undersized equipment reaching the rigging loft.
Why Chain Measurement Matters
Lifting chains are specified by diameter, not by the dimensions of the link opening or any other visible feature. The diameter of the wire that forms each link determines the Working Load Limit (WLL), and the WLL determines whether a chain is legal and safe under LOLER 1998.
A Grade 80 chain and a Grade 100 chain of identical physical diameter carry very different loads. Grade 100 offers approximately 25% higher WLL than Grade 80 at the same diameter, which means chains that look alike may be rated for entirely different applications.
Measuring the diameter alone is not enough if the grade is unknown.
Every chain used for overhead lifting in the UK must carry clear grade markings and a certified WLL. If those markings are absent, the chain should not be used for lifting, regardless of how it looks.
The Four Key Measurements
When specifying a lifting chain, four dimensions fully define it.
Wire Diameter: This is the primary chain measurement, and the figure from which everything else follows. It is the thickness of the steel bar that forms each individual link, taken with a vernier calliper on the side of the link, away from the weld, perpendicular to the wire. A 10 mm chain measures 10 mm. A 13 mm chain measures 13 mm. These figures correspond directly to the capacity columns in any standard chain-link size chart.
Inside Length (Pitch) Pitch is the internal length of a single link, measured from the inside of one curved end to the inside of the other. It determines whether the chain will engage correctly with hooks, shortening clutches, and master links in the assembly. A mismatch here causes binding or incorrect seating under load.
Inside Width Inside width is the gap across the interior of the link at its widest point. It dictates which hooks and fittings will pass through cleanly and seat securely. A link with insufficient inside width may fit loosely, creating instability at the point of connection.
Overall Link Length The outside length of a link, measured from one curved end to the other, gives the external profile of the chain. This is relevant when calculating working length for multi-leg sling assemblies and confirming the rigging configuration fits the available height.
How to Measure Chain Link Size: Step by Step
The correct tool for this job is a vernier calliper or a digital calliper. A steel ruler is not precise enough; even a small reading error can result in specifying the wrong chain sizes and a WLL mismatch. Anyone responsible for procurement should know how to measure chain link size before confirming an order, rather than relying solely on supplier descriptions.
Step 1 | Select an undamaged section. Choose several links from the working length, away from the end fittings. Avoid links showing visible wear, distortion, or corrosion.
Step 2 | Measure the wire diameter. Position the calliper jaws around the wire of a link, away from the weld point. Record the reading in millimetres and repeat on at least three links to average the result.
Step 3 | Measure the inside length. Use the internal jaws to measure between the inner faces at each end of the link. This confirms the pitch.
Step 4 | Measure the inside width. Still using the internal jaws, measure across the interior at the widest point to confirm which fittings will seat correctly.
Step 5 | Cross-reference with a chain link size chart. Match the wire diameter against a grade-specific chart to confirm the WLL. Compare pitch and inside width against the hook and hardware specifications to confirm compatibility before ordering.
Reading a Chain Link Size Chart
A chain link size chart lists standard dimensions for each nominal chain size, organised by grade. The most important columns for lifting applications are the wire diameter and the WLL at vertical lift. A typical Grade 80 chart lists the following nominal wire diameters and single-leg WLLs:
|
Wire Diameter |
Single-Leg WLL (Grade 80) |
|---|---|
|
7 mm |
1,500 kg |
|
8 mm |
2,000 kg |
|
10 mm |
3,150 kg |
|
13 mm |
5,300 kg |
|
16 mm |
8,000 kg |
Grade 100 chains at the same diameters carry approximately 25% higher WLLs. Always verify exact figures against the documentation supplied with the specific chain rather than a generic reference.
The sling angle in multi-leg assemblies also reduces the effective WLL. At 30 degrees from the vertical, only half the single-leg rated capacity remains available per leg.
This reduction applies regardless of whether the chain itself is correctly sized, and it is a frequent cause of underspecified lifts where the chain measurement appears correct, but the rigging configuration is not.
Common Measurement Errors
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Measuring at the weld point. The weld on a chain link sits slightly wider than the surrounding wire. Taking a diameter reading here produces an inflated figure, leading to a lower-capacity chain being selected than the application requires.
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Using worn links as the reference. Chain links lose diameter through abrasion over their working life. A chain that originally measured 10 mm may read 9.5 mm or less after heavy use. If the reading falls below the manufacturer's minimum discard diameter, the chain must be withdrawn from service.
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Ignoring the grade marking. Wire diameter tells you the physical chain size, but not the grade. Two chains of identical diameter can carry very different WLLs. The grade stamp on the link must be checked alongside the measurement.
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Relying on packaging labels alone. Chain sizes on labels should be verified against the physical chain, particularly for older stock or chains moved between sites. Mislabelling does occur, and the consequences in a lifting application are serious.
Marking, Certification, and Replacement
Under LOLER 1998, every chain used for lifting in the UK must be clearly marked with its WLL and accompanied by a certificate of conformity. The grade marking is stamped into the steel links at regular intervals. If markings are illegible, the chain must be withdrawn from service until a competent person can verify its identity and certify its capacity.
LOLER also requires that lifting accessories, including chain slings, be thoroughly examined at intervals not exceeding 6 months. Dimensional checks, particularly wire diameter measurements, form part of that examination record.
Measurement is also the primary trigger for chain replacement. When the wire diameter of any link has reduced to 90% of the nominal new diameter, the chain must be taken out of service.
For a 10 mm chain, that means a measured diameter of 9 mm or less signals the end of safe service life. Stretching is a separate criterion: if ten consecutive links measure more than 5% over the manufacturer’s specified pitch length, the chain has elongated and must be replaced.
Choosing the Right Chain
Once the chain measurement is confirmed and the grade verified, selection comes down to matching the WLL to the load, accounting for the number of legs and the sling angle, and confirming all fittings are compatible with the chain's inside dimensions.
For teams procuring a new sling assembly, buying a complete certified assembly removes several of these variables. The manufacturer's certificate confirms that the chain, master link, hooks, and shortening clutches have been assembled, tested, and rated as a single unit to the required standard.
Velebit Lifting supplies a full range of Grade 80 and Grade 100 chain slings, available in single, double, three-leg, and four-leg configurations, all supplied with LOLER-compliant certification.
Whether you need help reading a chain link size chart, confirming hardware compatibility, or selecting the right chain sizes for a specific application, the team is available to advise before you place an order.
Browse the full range at Velebit Lifting, or contact the team directly for guidance on chain measurement, specifications, and compliant procurement for UK lifting operations.