NIOSH lifting equation

Measure the task, not just the object

Use the hand positions and lift conditions requested by the form. Where control at the destination matters, check that position too. Frequency and duration describe exposure over time; a single observed lift may not represent the full job. This implementation evaluates a single task, not a composite of different lifting jobs.

Use the index to identify changes

A higher index indicates greater concern within the equation's scope. The result is not an individual's safe lifting capacity or a guarantee against injury. Tasks outside the supported conditions need a suitable ergonomic assessment rather than forcing their measurements into the equation.

Reading the task multipliers

The equation begins with a load constant and reduces it through multipliers describing the represented task. Reaching farther away, changing vertical position, twisting, repeating lifts, or having a less favorable grip can change the recommended weight limit. The load constant is not a general safe lifting limit to apply without those task conditions.

The lifting index compares the entered load with the calculated recommended weight limit. If the entered load doubles while every task factor stays the same, the index doubles. That comparison can help evaluate a proposed change, such as reducing load mass or bringing the hands closer to the body. Change one condition at a time to see which factor is limiting in the represented task. Measurements should describe normal working conditions and meaningful variations, not just a carefully arranged demonstration. Carrying, one-handed handling, unstable loads, and tasks outside the equation's applicability need other assessment methods. The worksheet does not combine multiple distinct tasks into a composite lifting index or determine an individual's medical fitness.

Formula

RWL = 23 kg × HM × VM × DM × AM × FM × CM. LI = load / RWL. Frequency table is interpolated; H and D have a 25 cm floor.