NIOSH Lifting Equation - Calculating Recommended Weight Limit (RWL)

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What is the Revised NIOSH lifting equation?

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The equation is:

LC x HM x VM x DM x AM x FM x CM = RWL 

where LC is the load constant (23 kg) and other factors in the equation are:

  • HM, the Horizontal Multiplier factor
  • VM, the Vertical Multiplier factor
  • DM, the Distance Multiplier factor
  • FM, the Frequency Multiplier factor
  • AM, the Asymmetric Multiplier factor
  • CM, the Coupling Multiplier factor
  • RWL, the Recommended Weight Limit

For each value, look up the corresponding factor and use this number in the equation. 

NOTE: Please see this alternate page for a functioning calculator.  

See Assessing Relevant Handling Factors for an explanation of terms.

Horizontal Multiplier (HM): Horizontal distance (H, in cm) from the midpoint between the ankles to the hands while holding the object.

H = Horizontal Distance (cm)HM Factor
25 or less1.00 

Vertical Multiplier (VM): The vertical distance (V, in cm) of the hands from the ground at the start of the lift.

V = Starting Height (cm)VM Factor
 30  0.87
 50 0.93 
 70  0.99 
 100  0.93 
 150  0.78 
 175 0.70
 >175 0.00

Distance Multiplier (DM): The vertical distance (D, in cm) that the load travels.

D = Lifting Distance (cm)DM Factor
25 or less1.00
 40  0.93 
 55  0.90
 100  0.87 
 145 0.85 
 175 0.85
 >175 0.00

Asymmetric Multiplier (AM): The twisting angle (A) of the body while lifting, measured in degrees.

A = Angle (degrees)AM Factor
90° 0.71 
 60°  0.81
 45°  0.86 
 30° 0.90
 0° 1.00

Frequency Multiplier (FM): The frequency (F) of lifts and the duration of lifting (in minutes or seconds) over a workshift.

F = Time Between Lifts FM Factor
Lifting While Standing:OR Lifting While Stooping:
One Hour or LessOver One HourOne Hour or LessOver One Hour
5 min1.000.851.000.85
1 min 0.940.750.940.75
30 sec0.910.650.910.65
15 sec0.840.450.840.45
10 sec0.750.270.750.27
6 sec0.450.130.45-
5 sec0.37 -0.37 -

Coupling Multiplier (CM): The quality of grasp (or coupling, C) classified as good, fair or poor and depends on the body position (either standing or stooping).

C = GraspCM Factor:
Good (handles)1.001.00

  • Fact sheet last revised: 2023-04-26