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> Calculating Recommended Weight Limit (RWL)

What is the Revised NIOSH lifting equation?
Where can I get more information 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),

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, and
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 explanation of terms.

To use the "automatic" calculator, click on the values for each factor in the left hand column (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.

H = Horizontal Distance (cm)	HM Factor
25 or less	1.00
30	0.83
40	0.63
50	0.50
60	0.42

Vertical Multipler (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

Distance Multipler (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

Asymmetric Multipler (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 Multipler (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		Lifting While Stooping
	One Hour or Less	Over One Hour	One Hour or Less	Over One 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 (A) and (B).

(A) Time Between Lifts
Lifting While Standing
One Hour or Less
Over One Hour
Lifting While Stooping
One Hour or Less
Over One Hour

(B) FM

Coupling Multipler (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 = Grasp	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 (A) and (B).

(A)Standing
Stooping

(B) CM

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.

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> Calculating Recommended Weight Limit (RWL)