Biomechanics Calculator | Industrial Engineering Calculators

Ergonomic Assessment Tools

These tools help evaluate biomechanical stresses in occupational tasks to prevent musculoskeletal disorders and injuries.

Moment/Torque

NIOSH Lifting

Static Strength

Moment (Torque) Calculator

Calculate the torque generated by a force acting at a distance from a pivot point, which is critical for analyzing joint stresses in ergonomic assessments.

Moment = Force × Distance × sin(θ)

Diagram of moment/torque calculation

Force (N or lb):

Distance (m or in):

Angle (degrees, 90° = perpendicular):

Units:

Moment/Torque Result

Calculated Moment:

Interpretation

This moment represents the rotational force at the joint. Compare to:

Joint	Typical Maximum Moment (N·m)	Typical Maximum Moment (lb·in)
Shoulder	40-60	350-530
Elbow	25-35	220-310
Wrist	8-12	70-105
Lumbar Spine (L5/S1)	120-180	1060-1590

NIOSH Lifting Equation Calculator

The NIOSH equation calculates a Recommended Weight Limit (RWL) and Lifting Index (LI) for two-handed manual lifting tasks.

RWL = LC × HM × VM × DM × AM × FM × CM
Lifting Index (LI) = Object Weight / RWL

Task Parameters

Object Weight (kg or lb):

Units:

Horizontal Location (cm or in):

Vertical Start (cm or in from floor):

Vertical End (cm or in from floor):

Lifts per Minute:

Duration:

Coupling Type:

Asymmetry Angle (degrees, 0° = symmetric):

NIOSH Lifting Results

Horizontal Multiplier (HM)

Vertical Multiplier (VM)

Distance Multiplier (DM)

Asymmetric Multiplier (AM)

Frequency Multiplier (FM)

Coupling Multiplier (CM)

Recommended Weight Limit (RWL)

Lifting Index (LI)

Interpretation

Lifting Index (LI)	Risk Level	Action Required
LI ≤ 1	Low	Acceptable for most workers
1 < LI ≤ 2	Moderate	Evaluate task and consider improvements
2 < LI ≤ 3	High	Implement changes to reduce risk
LI > 3	Very High	Immediate changes required

Static Strength & Compressive Force Calculator

Estimate the required strength and spinal compressive forces for static holding tasks, particularly at the L5/S1 joint.

Compressive Force = (Weight × Distance) / (Back Muscle Moment Arm) + Upper Body Weight

Diagram of spinal compressive forces

Load Weight (kg or lb):

Units:

Horizontal Distance (cm or in from spine):

Upper Body Weight (kg or lb, approx. 55% total):

Torso Angle (degrees from vertical):

Arm Angle (degrees from vertical):

Static Strength Results

Required Back Muscle Force

L5/S1 Compressive Force

Interpretation

Compressive Force	Risk Level	NIOSH Limit
< 3400 N (765 lb)	Low	Acceptable for most workers
3400-6400 N (765-1440 lb)	Moderate	Some risk for some workers
> 6400 N (1440 lb)	High	Unacceptable for most workers

Reduction Strategies

Reduce load weight
Keep load closer to the body
Minimize torso flexion (bending forward)
Use lifting aids or team lifting
Rotate workers to limit exposure

Practical Examples

Example 1: Safe Lifting

Scenario: Lifting 10 kg box from waist height (75cm) to shelf (120cm), close to body (25cm horizontal), good grip, 4 lifts/minute for 2 hours.

Results: RWL = 14.2 kg, LI = 0.7 (Safe)

Example 2: Risky Lifting

Scenario: Lifting 25 kg crate from floor (30cm) to waist height (75cm), 50cm horizontal distance, poor grip, 6 lifts/minute for 8 hours.

Results: RWL = 7.8 kg, LI = 3.2 (Very High Risk)

Example 3: Static Holding

Scenario: Holding 15 kg tool 40cm in front of body with 30° torso flexion for extended periods.

Results: Compressive Force = 4200 N (Moderate Risk)