NIOSH Calculator
NIOSH lifting equation calculator
This NIOSH lifting equation calculator applies the Revised NIOSH Lifting Equation to one lifting task: enter the load and where, how far and how often it is lifted, and it returns the recommended weight limit (RWL) and the lifting index (LI), the load divided by that limit. The equation is an assessment tool published by the US National Institute for Occupational Safety and Health; it is not a law and not a product approval, and its load constant of 23 kg is the ceiling under ideal conditions, with every departure from ideal bringing the limit down. The result shows how far a workstation sits from the recommended limit before any equipment is chosen; what to lift the load with is a separate question, answered for the load types we handle.
Inputs
Six inputs are required. The asymmetry angle and the coupling are optional in this form but are full multipliers in the equation: leave them blank only if the load is lifted straight in front of the body with a fair grip, and the result table says when a default has been used. Measure H, V and A at the origin of the lift, where the hands take the load: H from the mid-point between the ankles to the hands, V from the floor to the hands, A as the angle the load sits off the plane straight in front of the body; D is the height of the hands at the destination minus their height at the origin, and F is the average number of lifts per minute over a 15-minute period. The values already in the form are the example worked out below, a 25 kg sack picked from a low pallet.
What the index means and does not mean
The index is a screening figure for one two-handed lifting task under the equation's assumptions. The manual lists the conditions it does not cover: lifting or lowering with one hand, for more than 8 hours, while seated or kneeling, in a restricted space, of unstable objects such as partly filled bags or containers of liquid, while carrying, pushing or pulling, with wheelbarrows or shovels, at high speed, with poor footing, or in hot, cold or humid conditions outside about 19–26 °C or 35–50% relative humidity. For those tasks the equation does not apply, and the calculator cannot detect them; check them yourself. When H, V, D, A or the frequency is beyond the equation's limits, that multiplier is zero and so is the recommended weight limit: no load is recommended for the task as entered; and if the hands end above 175 cm, the task is outside the equation's vertical range.
It is not a product approval: the lifting equation assesses a task, not a product, so no lifter can carry an approval on the strength of it, and a lifter that takes the weight out of the task does not by itself settle the workstation's compliance; the employer's risk assessment, operator training and local inspection rules still apply. For a formal assessment, use NIOSH's own tools or have your EHS team run the full analysis.
Condition: the equation is a US tool with no legal force of its own; the legal or guideline limits that apply in your country are on the weight limits by country page.
Result: RWL and lifting index
The recommended weight limit is the load the equation accepts for that task; the lifting index divides your load by it. An index above 1 means the load is above the recommended limit for the task and the risk is raised for some workers; the greater the index, the smaller the share of workers able to sustain the task, which is why the index is used to rank tasks for redesign. The figure is an estimate for one task at the origin of the lift; the manual's full method also looks at the destination where the load must be placed precisely, and at multi-task jobs.
Next step: see how the recommended limit compares with the legal or guideline limit in your country on the weight limits by country page, see a worked risk assessment that uses the same inputs, and read why OSHA and the NIOSH equation are not the same thing; then tell us the load and the station.
the load, the pick and place heights and the lifts per hour are the same questions the enquiry form asks.
Formula and multipliers
The recommended weight limit is the load constant times six multipliers, each between zero and one, as published in the NIOSH Applications Manual for the Revised NIOSH Lifting Equation:
RWL = LC × HM × VM × DM × AM × FM × CM, with LC = 23 kg (51 lb)
| Multiplier | Formula or table | Range and cut-off |
|---|---|---|
| HM, horizontal | 25 / H, with H in cm | H of 25 cm or less counts as 25 cm, so HM = 1; H above 63 cm gives HM = 0 |
| VM, vertical | 1 − 0.003 × the difference between V and 75 cm, ignoring the sign | VM = 1 at 75 cm, 0.78 at floor level, 0.70 at 175 cm; V above 175 cm gives VM = 0, at the origin or at the destination |
| DM, distance | 0.82 + 4.5 / D, with D in cm | D below 25 cm counts as 25 cm, so DM = 1; DM = 0.85 at 175 cm; D above 175 cm gives DM = 0 |
| AM, asymmetry | 1 − 0.0032 × A, with A in degrees | A from 0° to 135°; A above 135° gives AM = 0 |
| FM, frequency | Table 5 of the manual: lifts per minute against work duration of up to 1, 2 or 8 hours, each split at V = 75 cm (30 in) | F from 0.2 to 15 lifts per minute; below 0.2 counts as 0.2; above the table's maximum for the duration and height the limit is zero; values between table rows are interpolated, as the manual instructs |
| CM, coupling | Table 7 of the manual: good 1.00; fair 0.95 below 75 cm and 1.00 at or above; poor 0.90 | Grip quality classed by Table 6; a non-rigid bag that sags in the middle counts as poor |
Source and version: the formulas and cut-offs, the values of Tables 5 and 7 and the classification in Table 6 are taken from NIOSH Publication 94-110, Applications Manual for the Revised NIOSH Lifting Equation, 1994; the September 2021 revision gives the same constant and multipliers. Checked against the manual on 20 October 2026.
Worked example: a 25 kg sack
Example task (estimate): a 25 kg sack picked from a low pallet with the hands 15 cm above the floor and 45 cm in front of the ankles, placed on a conveyor 90 cm high, a vertical travel of 75 cm, with the load 30° to the side of straight ahead, three lifts a minute for more than two hours, and a fair grip on a firm, well-filled sack.
| Multiplier | Value | From |
|---|---|---|
| HM | 25 / 45 ≈ 0.56 | H = 45 cm |
| VM | 1 − 0.003 × 60 = 0.82 | V = 15 cm, 60 cm below the 75 cm optimum |
| DM | 0.82 + 4.5 / 75 = 0.88 | D = 75 cm |
| AM | 1 − 0.0032 × 30 ≈ 0.90 | A = 30° |
| FM | 0.55 | Table 5: 3 lifts a minute, more than 2 up to 8 hours, V below 75 cm |
| CM | 0.95 | Table 7: fair coupling, V below 75 cm |
RWL ≈ 23 × 0.56 × 0.82 × 0.88 × 0.90 × 0.55 × 0.95 ≈ 4.4 kg, and LI ≈ 25 / 4.4 ≈ 5.7 (estimate). If the sack sags in the middle, the manual classes the coupling as poor, CM becomes 0.90, RWL about 4.1 kg and LI about 6.1. Either way the task sits at roughly five to six times the recommended limit, which is the kind of task a vacuum bag lifter for 25 kg sacks is chosen for, where the sack surface lets the pad seal.
Next step
A high index is a reason to avoid the hazardous manual lift, typically with a mechanical aid, rather than to rely on lifting technique; avoiding it is the first step most OSH rules ask for. Send us the same figures: load weight, pick and place heights, lifts per hour and a sketch or photo of the station; they are what we need to start, we then ask about the packaging, the environment and the site, and propose a vacuum tube lifter and the crane or rail to carry it.
Cowest Machinery designs and manufactures vacuum tube lifters at its factory in Qingyuan, Guangdong, China.