Ergonomic Risk Assessment Calculator
Calculate RULA/REBA-inspired ergonomic risk scores and strain index from workplace posture and force data.
About this calculator
This calculator produces simplified, RULA/REBA/Strain-Index-inspired ergonomic risk estimates from six task ratings. RULA (Rapid Upper Limb Assessment) and REBA (Rapid Entire Body Assessment) are established observational ergonomics assessment methods developed by researchers (McAtamney & Corlett for RULA; Hignett & McAtamney for REBA) and widely used in workplace safety practice -- but note that OSHA itself does not currently enforce a specific numeric ergonomics standard in the US (a 2000 ergonomics rule was rescinded in 2001); ergonomic hazards are instead typically addressed under OSHA's General Duty Clause, with RULA, REBA, and the Strain Index serving as independent, non-regulatory assessment tools rather than literal OSHA-mandated thresholds. This calculator's RULA Score and REBA Score are simplified single-number approximations of those real multi-body-part methodologies (which in full form separately score the neck, trunk, upper arm, forearm, wrist, and legs); increasing Posture Score, Force Level, Repetition Level, or Task Duration each raise RULA Score, since worse posture, higher force, more frequent repetition, and longer daily exposure duration all compound risk together.
The Strain Index (following Moore & Garg's simplified model) estimates hazard from Force Level and Repetition Level specifically -- both raise it -- while Vibration Exposure and Contact Stress have no effect on Strain Index at all, since the Strain Index methodology doesn't model those factors; they instead only affect RULA Score and REBA Score. Strain Index Assessment flags "Hazardous" above a Strain Index of 7, a commonly cited cutoff in the ergonomics literature. Treat every score here as a screening-level estimate to help prioritize which tasks deserve a closer look, not a substitute for a trained ergonomist's full observational assessment or a specific regulatory determination.
Inputs
Results
RULA Score (1-7)
4.5
Risk Level
Medium
How to Use This Calculator
- Rate Posture Score (1=neutral, 5=extreme deviation from neutral) based on the worker's typical posture during the task.
- Rate Force Level (1=light, under 2 lbs, to 5=heavy, over 20 lbs) and Repetition Level (1=infrequent to 5=constant high-frequency).
- Enter Task Duration in hours per day, and select whether Vibration Exposure or Contact Stress apply.
- Review RULA Score, Risk Level, REBA Score, and Strain Index Assessment together — they're independent estimates, not identical scales.
- Use Action Priority to decide how urgently engineering or administrative controls are needed for this task.
How the result changes with Task Duration (hours/day)
| Task Duration (hours/day) | RULA Score (1-7) | Risk Level |
|---|---|---|
| 3 | 3 | Low |
| 4.5 | 4.5 | Medium |
| 9 | 6 | Medium |
| 12 | 6 | Medium |
What each input means
- Posture Score
- 1=Neutral, 5=Extreme deviation from neutral posture.
- Force Level
- 1=Light (<2 lbs), 5=Heavy (>20 lbs).
- Repetition Level
- 1=Infrequent, 5=Constant high-frequency repetition.
- Task Duration (hours/day)
- Hours per day performing this task.
- Vibration Exposure
- Whether the task involves vibrating hand tools or equipment.
- Contact Stress
- Whether hard or sharp edges press against the body during the task.
How this is calculated
Worked example, using the default values
- Identify Input Parameters6 parametersPosture Score = 3, Force Level = 3, Repetition Level = 3, Task Duration (hours/day) = 6, Vibration Exposure = 0, Contact Stress = 0 = 6 input(s) provided
- Calculate RULA ScoreRULA Score4.5 = 4.5
- Calculate Risk Level3 = 3
- Calculate REBA ScoreREBA Score15 = 15
- Calculate Strain IndexStrain Index20.3 = 20.3
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Is this calculator's risk score an official OSHA requirement?
No -- OSHA does not currently enforce a specific numeric ergonomics standard in the US (a 2000 ergonomics rule was rescinded by Congress in 2001). RULA, REBA, and the Strain Index are independent, widely used ergonomics assessment methodologies developed by researchers, not OSHA-mandated thresholds. OSHA typically addresses ergonomic hazards case by case under its General Duty Clause rather than a specific numeric rule.
Why don't Vibration Exposure and Contact Stress affect the Strain Index?
The Strain Index methodology (following Moore & Garg's model) is built specifically from intensity of effort, frequency of exertion, posture, and duration -- it doesn't include a vibration or contact-stress term. Both factors do still affect RULA Score and REBA Score, methodologies that were designed with additional risk factors like these in mind.
Why do RULA Score and REBA Score sometimes disagree on risk level?
RULA and REBA are two independent, differently weighted assessment methods -- RULA focuses more on the upper limbs, while REBA covers the entire body and weighs force and posture somewhat differently. Both are simplified here into single-number approximations, so treat disagreement between them as a signal to look more closely rather than a contradiction to resolve.
What should I do if Action Priority shows "Immediate"?
An Immediate priority means the combined risk score is at the high end of the range this calculator estimates, suggesting the task's posture, force, repetition, and duration combine into meaningful ergonomic risk. Real-world next steps typically include a closer observational assessment (ideally by a trained ergonomist) and consideration of engineering controls (tool or workstation redesign) or administrative controls (task rotation, rest breaks) to reduce exposure.
How were the RULA, REBA, and Strain Index scoring rules simplified here?
The full RULA and REBA methods separately score multiple body regions (neck, trunk, upper arm, forearm, wrist, legs) using detailed posture diagrams and combine them through lookup tables. This calculator condenses that into a single overall Posture Score, Force Level, and Repetition Level rating, which makes it faster to use for a quick screen but less precise than a full body-region-by-body-region assessment.
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