Liberty Mutual manual handling tables Snook Tables Calculator

Check a lifting, lowering, pushing, pulling or carrying task against the Snook Tables. Describe the task, and the calculator gives the design goal weight or force and, with the actual weight or force, the risk index.

How to use the Snook Tables calculator

1. Choose the task: lift or lower, push, pull or carry. For a job with several tasks, assess each one.
2. Choose the units for the weights and forces you will enter.
3. Describe the task (step 3). For a lift or lower, choose the zone, how far out from the body the hands are and how far the load moves. For a push or pull, choose the height of the hands and the distance. For a carry, choose the carrying height and distance. Then choose how often the task is done.
4. Read the design goal, the weight or force that 75% of women find acceptable for that task.
5. Enter the actual weight or force (step 4) to get the risk index. For pushing and pulling, measure the initial and sustained forces with a force gauge.
6. Print or save the result as a PDF to keep a record, or start over to assess another task.

For a full walkthrough with five worked examples, read our step-by-step guide to the Snook Tables or the Snook Tables lesson in Mastering Ergonomics.

How the design goal and risk index work

The Snook Tables come from psychophysical studies at the Liberty Mutual Research Institute, in which workers adjusted the load to the most they could handle without strain or unusual fatigue. Thomas E. Bernard of the University of South Florida adapted the tables into design goals, choosing the weight or force acceptable to 75% of women as the target so that nearly all workers are protected.

• Design goal: the acceptable weight or force for the task, from the tables. It falls as the task is done more often, over a greater distance, farther from the body, or above the shoulder or below the knuckles.
• Risk index: the actual weight or force divided by the design goal. A risk index of 1.0 or lower is within the design goal; above 1.0, redesign the task.
• Out of range: no weight or force is acceptable at that combination of distance and frequency, so the task needs to change.

Snook Tables examples

These are two of the worked examples from our Snook Tables guide.

Above-shoulder lift

A worker lifts a 32 lb load from a cart at 25 in to a rack at 55 in, a lift of 30 in that ends above the shoulder, with the hands 10 in in front of the body, once every 5 minutes. The design goal is 18 lb, so the risk index is 32 divided by 18, or 1.78: above the design goal. Load this example into the calculator.

Push

A worker pushes a cart 97 ft with the hands at about 36 in, once every 5 minutes. A force gauge reads 24 lb to get it moving and 15 lb to keep it moving. The design goals are 40 lb initial and 20 lb sustained, so the risk indexes are 0.60 and 0.75: within the design goal. Load this example into the calculator.

When to use the Snook Tables

The Snook Tables are the method to use for pushing, pulling and carrying. For two-handed lifting and lowering with exact hand measurements, the NIOSH Lifting Equation is more detailed, and the WISHA Lifting Calculator is a quick screening check. To score the posture during the task, use the REBA calculator.

Save and track manual handling assessments

This calculator does not save your results. ErgoPlus ergonomics software keeps every Snook Tables assessment with its photos and notes, compares tasks across worksites and tracks improvements over time.

Source: Snook, S. H. and Ciriello, V. M. (1991). The design of manual handling tasks: revised tables of maximum acceptable weights and forces. Ergonomics, 34(9), 1197–1213; design goals adapted by Thomas E. Bernard, University of South Florida.