NASA Task Load Index (TLX)

The Official NASA Task Load Index (TLX) is a subjective workload assessment tool developed by Human Systems Integration Division researchers. This tool allows users to perform subjective workload assessments on operator(s) working with various human-machine interface systems. Originally developed as a paper and pencil questionnaire by NASA Ames Research Center’s (ARC) Sandra Hart in the 1980s, NASA TLX has become the gold standard for measuring subjective workload across a wide range of applications. 

By incorporating a multi-dimensional rating procedure, NASA TLX derives an overall workload score based on a weighted average of ratings on six subscales: 

• Mental Demand
• Physical Demand
• Temporal Demand
• Performance
• Effort
• Frustration 

NASA TLX has been successfully used around the world to assess workload in various environments such as aircraft cockpits; command, control, and communication (C3) workstations; supervisory and process control; and simulations and laboratory tests. 

Paper and Pencil Version

If you would like to use the NASA TLX tool, but do not want to use the iOS app, it is available here in its original paper and pencil format. This tool is just as powerful as the computerized version, and will be just as helpful in your workload analysis. Before you use the scale, however, be sure to download and thoroughly review the instruction manual.

This will ensure that you are using the scale correctly and will allow you to accurately decipher the data you collect. For example, you will find the comparison cards to use in conjunction with the TLX Scale inside the instruction manual. 

The NASA TLX tool is “open source”, and is therefore available for immediate use by any person or organization (worldwide). It is not necessary to obtain permission from NASA to use TLX, nor is permission needed to make modifications to the tool itself (i.e. language translation). 

TLX iOS App

The NASA TLX iOS app is available for immediate use by any person or organization (worldwide). It is not necessary to obtain permission from NASA to use the TLX iOS app.

The NASA TLX tool is available as an iOS app that helps researchers evaluate their workloads, on the go. 

Since the 1980’s, the gold-standard subjective workload assessment tool was pencil and paper questionnaires to conduct assessments of workload scores on Mental Demands, Physical Demands, Temporal Demands, Own Performance, Effort, and Frustration. The legacy version, available only on Windows NT/XP desktop computers, is in the top 5 software downloads for the agency, and the top software download for Ames Research Center with an average of 1-3 download requests per week. 

“The Official NASA TLX app addresses a significant backlog of pent up demand from researchers looking for a workload measurement solution that integrates with their modern computer/research environments,” said Dr. Brian Gore, Deputy Element Scientist for the Human Factors and Behavioral Performance (HFBP) Element in the Human Research Program (HRP) and TLX project lead at Ames. “Now, users will be able to use their mobile devices (iPhone, iPad, and iPod touch) to collect subjective assessments of workload in a given operational context on a very easy-to-use platform.”

NASA TLX Contact Info.

For questions regarding the use of the NASA TLX paper/pencil version or the TLX app – Brian Gore

For technical questions regarding the Official NASA TLX iOS App – Elizabeth Wagstaff

For questions regarding the NASA TLX website – Phil So

NASA TLX Publications

The NASA TLX tool has been used world-wide to help researchers evaluate workload in various human-machine systems. To date, there have been many hundreds of studies and publications in which the tool has played an integral role in the research. 

Below you will find a number of TLX-related documents and publications, a number of which are available for you to download. 

* Please note, this webpage is not actively maintained and is for historical reference only.