Wire Rope SWL / Load Checker
Check whether a lift is within the rated capacity of a wire rope sling, chain, or item of lifting gear using the Working Load Limit (WLL / SWL) from its tag. Enter the tag rating, the applied load, and the number of rope parts supporting the load to get the total capacity, the percentage used, the capacity left, and a clear PASS / WARNING / OVERLOAD verdict.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Read the rated WLL (or SWL) directly off the gear tag, ID disc, or coloured sling label and enter it in kilograms — never guess or back-calculate it from a breaking load.
- Enter the actual load this item will carry in kilograms, including any allowance for angle, shared load, or dynamic (shock) effects.
- Enter the number of parts or falls of rope supporting the load (1 for a single direct part; 2 if the rope is reeved so two falls share the load, and so on). Leave blank for 1.
- Read the total capacity, utilisation percentage, remaining capacity, and the PASS / WARNING / OVERLOAD verdict.
How it works
Total capacity = tag WLL × number of parts, because each supporting part of rope carries its share of the load. Utilisation = applied load ÷ total capacity × 100, and remaining capacity = total capacity − applied load. The verdict is PASS at 90% or below, WARNING above 90% (getting close to the limit), and OVERLOAD above 100%. The calculator never invents a breaking load — it works only from the certified WLL on the gear.
Worked example
Worked example. A wire rope sling is tagged WLL 2000 kg and is used in a single part to lift 1500 kg. Total capacity = 2000 × 1 = 2000 kg. Utilisation = 1500 / 2000 × 100 = 75%, so 500 kg of capacity remains and the verdict is PASS. Reeve the same rope in 2 parts and the capacity doubles to 4000 kg, dropping utilisation to 37.5%.
Common mistakes
- Using a breaking load (MBL) instead of the WLL — the WLL already includes the design factor and is the only figure you load to.
- Forgetting that a sling at an angle, or one leg of a multi-leg sling, carries MORE than the straight vertical load, so the applied load figure must be the real load on that item.
- Counting parts wrongly — only count the rope falls that genuinely support the load; a becket or dead-end that is anchored does not add a working part.
Frequently asked questions
What is the difference between WLL and SWL?
They are effectively the same working figure for everyday use — the maximum load the item is rated to carry in service. Modern tags use WLL (Working Load Limit); older gear and some standards say SWL (Safe Working Load). Always use the value printed on the tag.
Why does adding parts increase the capacity?
When a rope is reeved so that several falls share the load, each part carries only its fraction of the total, so the combined capacity is the single-part WLL multiplied by the number of supporting parts — the same principle as a block and tackle.
Should I lift right up to 100% utilisation?
No. The WLL is a limit, not a target. Keep a margin, account for dynamic and angle effects, and never lift over people. A licensed rigger and the relevant standards (AS 1418 / AS 2550 / AS 4991) govern the actual lift plan.
Related tools
- Chain Sling WLL (Grade & Angle) Calculator
- WLL from Breaking Load & Safety Factor Calculator
- Sling Angle Load Factor Calculator
- Sling D/d Ratio Efficiency Calculator
- Crane Lift Utilisation Calculator
- Four-Leg Sling Load Share Calculator
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