Calculate working load limit (WLL or SWL) from minimum breaking load and a design factor, with typical factors for chain, wire rope, slings and straps.

The breaking strength from the manufacturer or standard, before any design factor.

Typical design factors from ASME B30.9, B30.26 and WSTDA. Your equipment’s tag or maker may differ.

Ratio greater than 1, such as 5 for 5:1. Filled from the equipment type; edit it to match your rating.

Optional applied load
Optional. Utilization compares this load with the entered or calculated WLL; it does not approve a lift.

Working Load Limit Formula

The following two example problems outline the steps and information needed to calculate the Working Load Limit.

WLL = MBL / SF

Variables:

  • WLL is the Working Load Limit (N)
  • MBL is the minimum breaking load (N) 
  • SF is the safety factor 

For this simplified arithmetic relationship, divide minimum breaking load by the applicable design factor. Actual equipment WLL comes from its manufacturer for the relevant configuration; this calculator does not select a factor or certify a lift.

How to Calculate Working Load Limit?

The following steps outline how to calculate the Working Load Limit.

  1. First, determine the minimum breaking load (N). 
  2. Next, determine the safety factor. 
  3. Next, gather the formula from above = WLL = MBL / SF.
  4. Finally, calculate the Working Load Limit.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

minimum breaking load (N) = 5,000

safety factor = 2.5

WLL = MBL / SF = 5,000 / 2.5 = 2,000 N. This arithmetic example does not establish manufacturer-rated capacity.