NIOSH Lifting Equation (revised)
NIOSH Lifting Equation - Calculating
Recommended Weight Limit (RWL)
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What is the Revised NIOSH lifting Where can I get more information
equation? about the lifting equation?
What is the Revised NIOSH lifting equation?
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. See
Assessing Relevant Handling Factors for an explanation of terms.
To use the calculator, click on the values for each factor (or you can input your numbers
directly into the second equation). Press the "Calculate RWL" button when you have finished
selecting all of the values.
Horizontal Multiplier (HM): Horizontal distance (H, in cm) from the midpoint between the
ankles to the hands while holding the object.
NIOSH Lifting Equation - Calculating Recommended Weight Limit (RWL) CCOHS
H = Horizontal Distance (cm) HM Factor
25 or less 1.00
30 0.83
40 0.63
50 0.50
60 0.42
Select the HM value: 30
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
0 0.78
30 0.87
50 0.93
70 0.99
100 0.93
150 0.78
175 0.70
>175 0.00
Select the VM value: 0
Distance Multiplier (DM): The vertical distance (D, in cm) that the load travels.
D = Lifting Distance (cm) DM Factor
25 or less 1.00
40 0.93
55 0.90
100 0.87
145 0.85
175 0.85
>175 0.00
NIOSH Lifting Equation - Calculating Recommended Weight Limit (RWL) CCOHS
Select the DM value: 25 or less
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
Select the AM value: 90°
Frequency Multiplier (FM): The frequency (F) of lifts and the duration of lifting (in minutes or
seconds) over a workshift.
FM Factor
F = Time Between Lifting While Standing: OR Lifting While Stooping:
Lifts
One Hour or Over One One Hour or Over One
Less Hour Less Hour
5 min 1.00 0.85 1.00 0.85
1 min 0.94 0.75 0.94 0.75
30 sec 0.91 0.65 0.91 0.65
15 sec 0.84 0.45 0.84 0.45
10 sec 0.75 0.27 0.75 0.27
6 sec 0.45 0.13 0.45 -
5 sec 0.37 - 0.37 -
FM = pick a value from both (A) and (B).
(A) Time Between Lifts
Lifting While Standing
NIOSH Lifting Equation - Calculating Recommended Weight Limit (RWL) CCOHS
One Hour or Less
Over One Hour
Lifting While Stooping
One Hour or Less
Over One Hour
(B) Select the FM value: 5 min.
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).
CM Factor:
C = Grasp
Standing Stooping
Good (handles) 1.00 1.00
Fair 1.00 0.95
Poor 0.90 0.90
CM = pick a value from both (A) and (B).
(A) Standing
Stooping
(B) Select the CM value: Good (handles)
The revised NIOSH Lifting Equation is: 23 Kg x HM x VM x DM x AM x FM x CM= RWL
23 Kg x x x x
x x =
or, input values directly in the equation below:
23 Kg x x x x
x x =
Where can I get more information about the lifting equation?
More information is available in other OSH Answer documents. Please see the other
documents in the NIOSH Lifting Equation series.
NIOSH Lifting Equation - Calculating Recommended Weight Limit (RWL) CCOHS
Fact sheet last revised: 2023-03-01
Disclaimer
Although every effort is made to ensure the accuracy, currency and completeness of the
information, CCOHS does not guarantee, warrant, represent or undertake that the information
provided is correct, accurate or current. CCOHS is not liable for any loss, claim, or demand
arising directly or indirectly from any use or reliance upon the information.
NIOSH Lifting Equation - Calculating Recommended Weight Limit (RWL) CCOHS
