Find the recommended weight limit for a lifting or lowering task and how risky the actual load is. Enter the load, how often and how long the lifting goes on, the grip and the hand positions, and the calculator works out the Revised NIOSH Lifting Equation as you type.
How to use the NIOSH Lifting Equation calculator
- Choose the units you measured in. Switching converts the values you have already entered.
- Enter the load (step 2). Use the average weight lifted, and the heaviest weight if it differs.
- Choose the frequency, duration and coupling (steps 3 to 5). Frequency is the average number of lifts per minute over a 15-minute sample. Duration is how long the lifting goes on before a break of light work.
- Measure the hands at the origin (step 6): how far out from the ankles they are (H), how high off the floor (V), and how far the load is twisted from straight ahead (A).
- Measure the height of the hands at the destination (step 7). The calculator works out the travel distance (D). If the worker has to place the load precisely, tick significant control and measure H and A at the destination too.
- Read the lifting index and recommended weight limit. The results table shows every multiplier at the origin and destination, so you can see which factor reduces the limit most.
- Print or save the result as a PDF to keep a record, or start over to assess another task.
For a full walkthrough with two worked examples, read our step-by-step guide to the NIOSH Lifting Equation, the guide to the recommended weight limit or the NIOSH lesson in Mastering Ergonomics.
How the recommended weight limit is calculated
The recommended weight limit starts from a load constant of 51 lb (23 kg), the weight nearly all healthy workers can lift under ideal conditions. Each task variable then multiplies it by a factor of 1 or less:
RWL = LC × HM × VM × DM × AM × FM × CM
| Multiplier | Based on | Equal to 1 when |
|---|---|---|
| Horizontal (HM) | How far the hands are from the ankles | 10 in (25 cm) or closer |
| Vertical (VM) | How high the hands are off the floor | 30 in (75 cm), about knuckle height |
| Distance (DM) | How far the load travels vertically | 10 in (25 cm) or less |
| Asymmetric (AM) | How far the load is twisted from straight ahead | 0° |
| Frequency (FM) | Lifts per minute and the lifting duration | 0.2 lifts a minute or fewer, for 1 hour or less |
| Coupling (CM) | How well the hands can grip the load | Good coupling |
The lifting index is the actual load divided by the recommended weight limit. A lifting index of 1.0 or less is a nominal risk for most healthy workers. Above 1.0 the risk increases for some workers, and above 3.0 NIOSH considers many workers to be at high risk.
NIOSH Lifting Equation example
This is the warehouse pick example from our NIOSH guide. A worker lifts 28 lb containers from a rack pallet to a picking cart, once every 2 minutes over an 8-hour shift. The containers have good handholds. At the origin the hands are 15 in out and 12 in off the floor, twisted 30°, and they end 42 in off the floor at the cart, a travel distance of 30 in. No significant control is needed at the cart.
- Multipliers at the origin: HM 0.67, VM 0.86, DM 0.88, AM 0.90, FM 0.81 and CM 1.00.
- Recommended weight limit: 51 lb times the multipliers gives 18.95 lb.
- Lifting index: 28 lb divided by 18.95 lb gives 1.48, an increased risk for some workers. Raising the pallet so the lift starts higher would bring the vertical multiplier, and the limit, up.
Load this example into the calculator.
When to use the NIOSH Lifting Equation
The equation suits two-handed lifting and lowering while standing, with a stable load and good footing. It does not cover one-handed lifting, lifting while seated or kneeling, or carrying, pushing and pulling; for those, use the Snook Tables. The WISHA Lifting Calculator is a quicker screening check, and the REBA calculator scores the whole-body posture during the lift.
Save and track lifting assessments
This calculator does not save your results and handles one lifting task at a time. ErgoPlus ergonomics software keeps every NIOSH assessment with its photos and notes, compares tasks across worksites and tracks improvements over time.
Source: Waters, T. R., Putz-Anderson, V., Garg, A. and Fine, L. J. (1993). Revised NIOSH equation for the design and evaluation of manual lifting tasks. Ergonomics, 36(7), 749–776; and the NIOSH Applications Manual for the Revised NIOSH Lifting Equation (publication 94-110).
FAQ
Common questions about the NIOSH Lifting Equation
What is the NIOSH Lifting Equation?
The Revised NIOSH Lifting Equation is a method from the US National Institute for Occupational Safety and Health for assessing two-handed lifting and lowering tasks. It starts from a load constant of 51 lb (23 kg) and reduces it for the hand position, height, travel distance, twisting, frequency, duration and grip. The result is the recommended weight limit (RWL) for the task, and the lifting index (LI) compares the actual load with it.
What is a good lifting index?
A lifting index of 1.0 or less means the task poses a nominal risk for most healthy workers, and that is the design goal. Above 1.0, the risk increases for some workers, and NIOSH considers a lifting index above 3.0 to put many workers at high risk. Redesign tasks to bring the lifting index to 1.0 or lower.
What does the recommended weight limit (RWL) mean?
The RWL is the weight that nearly all healthy workers could lift in that way over a shift without an increased risk of low back pain. Under ideal conditions it is 51 lb (23 kg). Every factor that makes the lift harder, such as reaching out, lifting from the floor, twisting or lifting often, multiplies it by a number less than 1.
When is significant control needed at the destination?
Significant control is needed when the worker has to place the load precisely, hold it at the destination, or guide it into position. In that case the equation is applied at both the origin and the destination, and the higher lifting index governs. If the load is simply released, only the vertical height at the destination is needed, to work out the travel distance.
Which lifting tasks can the NIOSH equation not assess?
The equation does not apply to one-handed lifting, lifting while seated or kneeling, lifting in a cramped space, lifting unstable loads such as liquids or people, very fast lifting, or lifting on slippery floors. It also does not cover carrying, pushing or pulling; for those, use the Snook Tables.
What are the frequency-independent RWL and lifting index?
The frequency-independent RWL (FIRWL) leaves out the frequency multiplier, giving the limit for a single, occasional lift. The frequency-independent lifting index (FILI) divides the maximum load by it. A FILI above 1.0 flags a problem with the heaviest lifts even when they are infrequent.
Is this NIOSH Lifting Equation calculator free?
Yes. There is nothing to sign up for, and you can print or save each result as a PDF. The calculator does not store your results and handles one lifting task at a time. To save assessments, compare tasks and track improvements over time, use ErgoPlus ergonomics software.
