NIOSH Lifting Equation Calculator
Recommended Weight Limit (RWL) & Lifting Index (LI)
Formula (NIOSH Revised 1991):
RWL = LC × HM × VM × DM × AM × FM × CM · Lifting Index = Load Weight ÷ RWL
Load Constant LC = 51 lbs (23 kg). LI ≤ 1.0 = safe for most workers. LI > 1.0 indicates increased injury risk.
Load Constant LC = 51 lbs (23 kg). LI ≤ 1.0 = safe for most workers. LI > 1.0 indicates increased injury risk.
⚠ Important — Screening Tool, Not a Compliance Substitute
The NIOSH equation is a screening tool that applies to two-handed, smooth, controlled lifting by healthy adult workers. It does NOT apply to one-handed lifts, lifts while seated, lifts in restricted postures, lifting people, lifts in extreme heat or cold, or unstable loads. Use the Composite Lifting Index for jobs with multiple distinct lifting tasks. For ergonomic compliance, consult a Certified Professional Ergonomist (CPE). The author and FieldSafetyTalk.com assume no liability for decisions made using this tool.
1. Load and Position
2. Posture & Frequency
Please enter valid values for all fields.
Recommended Weight Limit (RWL)
—
Lifting Index (LI)
—
load ÷ RWL
Multiplier breakdown
LC — Load Constant—
HM — Horizontal Multiplier—
VM — Vertical Multiplier—
DM — Distance Multiplier—
AM — Asymmetry Multiplier—
FM — Frequency Multiplier—
CM — Coupling Multiplier—
= RWL—
Source: Waters TR, Putz-Anderson V, Garg A, Fine LJ. (1993). Revised NIOSH equation for the design and evaluation of manual lifting tasks. Ergonomics 36(7):749–776. NIOSH Applications Manual, DHHS (NIOSH) Pub. 94-110.
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