Calculator Library / Safety
Enter the load, the hand positions, the frequency, and the grip to get the recommended weight limit and lifting index from the revised NIOSH lifting equation, and see which change would help most.
Tool
RWL = 23 kg × HM × VM × DM × AM × FM × CM
Enter the load and the hand positions at the start (origin) and the end (destination) of a two-handed lift. The calculator gives the recommended weight limit (RWL) at each end, the lifting index (LI), and which factor limits the lift most. Load the example to see a lift before and after a redesign.
H is the horizontal distance from the midpoint between the ankles to the midpoint between the hands. V is the height of the hands above the floor. The vertical travel distance D is worked out as the difference between the two V values. A is the angle between the body’s front and the load, measured at the origin and the destination.
Everything runs in your browser. Nothing is sent to a server, and entries are not saved between visits. The equation applies only to two-handed lifts that fit the conditions listed below on this page. The examples are made-up data.
Result
Picture
A multiplier of 1.00 does not reduce the limit. The lower the bar, the more that factor cuts the 23 kg starting load.
Instructions
The revised NIOSH lifting equation estimates the heaviest load that most healthy workers could lift in a given set of conditions for up to eight hours without an increased risk of lifting-related low back pain. It starts from a load constant of 23 kg (51 lb) in ideal conditions and reduces it with six multipliers for how far away the load is held, how high it is lifted from, how far it travels, how much the body twists, how often it is lifted, and how well it can be gripped.
This calculator works out the recommended weight limit (RWL) at the origin and the destination of a lift, the lifting index (LI = load ÷ RWL) at each end, and the factors that cut the limit most. It matches the worked example in the Ergonomics in Kaizen guide and the Workplace Risk Assessment guide.
| Factor | Formula (metric) | Notes |
|---|---|---|
| Load constant (LC) | 23 kg | The load for ideal conditions |
| Horizontal multiplier (HM) | 25 ÷ H | H in cm, from 25 to 63. HM is 1.00 if H is under 25 cm, and zero over 63 cm |
| Vertical multiplier (VM) | 1 − 0.003 × |V − 75| | V is the hand height in cm, 0 to 175. The best height is 75 cm (about knuckle height) |
| Distance multiplier (DM) | 0.82 + 4.5 ÷ D | D is the vertical travel in cm, 25 to 175. DM is 1.00 if D is under 25 cm |
| Asymmetric multiplier (AM) | 1 − 0.0032 × A | A is the angle of twist in degrees, 0 to 135. Zero over 135 degrees |
| Frequency multiplier (FM) | From a table of lifts per minute, duration, and height | Falls from 1.00 for rare lifts to zero for very frequent lifting |
| Coupling multiplier (CM) | 1.00, 0.95, or 0.90 by grip and height | Good, fair, or poor coupling |
| Recommended weight limit (RWL) | LC × HM × VM × DM × AM × FM × CM | Calculated at the origin and at the destination |
| Lifting index (LI) | Load ÷ RWL | Up to 1.0 acceptable; 1.0 to 3.0 increased risk; over 3.0 high risk |
The first pre-loaded example is a 25 kg part lifted from a low pallet to a press table once a minute for most of a shift, with a twist at the pallet and a fair grip. The recommended weight limit is 5.1 kg at the origin and 7.8 kg at the destination, so the lifting index is 4.9 at the origin and 3.2 at the destination. Both are above 1.0, and the origin is well above 3.0: a high-risk lift.
The second example is the same task after a redesign: a lift table brings the pallet to knuckle height and close to the operator, the part is split into 12.5 kg totes with handles, and the twist is removed. The limit rises to 14.4 kg at the origin and 13.7 kg at the destination, and the lifting index falls to 0.87 and 0.91. All numbers are illustrative.
The lifting index (LI) is the load divided by the recommended weight limit for the task. An LI of 1.0 or less means the task is within the recommended limit for most healthy workers. An LI above 1.0 means the task increases the risk of lifting-related low back injury, and an LI above 3.0 is generally treated as high risk. The calculator reports it at the origin and the destination and takes the higher.
Because the lift starts in one place and ends in another, and the demands differ at each end. NIOSH recommends checking both the origin and the destination (and the points between for large lifts). A pallet at floor level may be the worst end of the lift, and a high shelf the worst end of another.
Around 75 cm (about 30 inches) above the floor, roughly knuckle height for an average worker, where the vertical multiplier is 1.00. Lifting from the floor or above the shoulders reduces the limit, as does lifting from far away from the body.
No. The revised NIOSH lifting equation covers two-handed manual lifting and lowering only. For pushing, pulling, and carrying, other methods such as the Liberty Mutual tables are used. Check the conditions listed on this page before applying the equation.
Redesign the task, and use the calculator to compare options. The largest gains usually come from bringing the load closer to the body, raising it off the floor, removing twisting, reducing the frequency, adding handles, reducing the load, or adding mechanical help. Use the hierarchy of controls: eliminate or engineer the lift before relying on training.
No. The calculator runs entirely in your browser, nothing is sent to a server, and your entries are not saved when you leave the page.